<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://www.westlake.com/role/AccountsReceivableThirdParties" xlink:href="wlkp-20170930.xsd#AccountsReceivableThirdParties" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/AccountsReceivableThirdPartiesAccountsReceivablethirdPartiesScheduleOfAccountsReceivableDetails" xlink:href="wlkp-20170930.xsd#AccountsReceivableThirdPartiesAccountsReceivablethirdPartiesScheduleOfAccountsReceivableDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/AccountsReceivableThirdPartiesTables" xlink:href="wlkp-20170930.xsd#AccountsReceivableThirdPartiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/AccumulatedOtherComprehensiveIncomeLoss" xlink:href="wlkp-20170930.xsd#AccumulatedOtherComprehensiveIncomeLoss" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/AccumulatedOtherComprehensiveIncomeLossDetails" xlink:href="wlkp-20170930.xsd#AccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/AccumulatedOtherComprehensiveIncomeLossTables" xlink:href="wlkp-20170930.xsd#AccumulatedOtherComprehensiveIncomeLossTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/CommitmentsAndContingencies" xlink:href="wlkp-20170930.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/CommitmentsAndContingenciesDetails" xlink:href="wlkp-20170930.xsd#CommitmentsAndContingenciesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedBalanceSheets" xlink:href="wlkp-20170930.xsd#ConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:href="wlkp-20170930.xsd#ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedStatementsOfCashFlows" xlink:href="wlkp-20170930.xsd#ConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedStatementsOfChangesInEquity" xlink:href="wlkp-20170930.xsd#ConsolidatedStatementsOfChangesInEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedStatementsOfComprehensiveIncome" xlink:href="wlkp-20170930.xsd#ConsolidatedStatementsOfComprehensiveIncome" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedStatementsOfOperations" xlink:href="wlkp-20170930.xsd#ConsolidatedStatementsOfOperations" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DerivativeInstruments" xlink:href="wlkp-20170930.xsd#DerivativeInstruments" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DerivativeInstrumentsDetails" xlink:href="wlkp-20170930.xsd#DerivativeInstrumentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DerivativeInstrumentsIneffectivePortionDetails" xlink:href="wlkp-20170930.xsd#DerivativeInstrumentsIneffectivePortionDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DerivativeInstrumentsTables" xlink:href="wlkp-20170930.xsd#DerivativeInstrumentsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DescriptionOfBusinessAndBasisOfPresentation" xlink:href="wlkp-20170930.xsd#DescriptionOfBusinessAndBasisOfPresentation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DescriptionOfBusinessAndBasisOfPresentationDetails" xlink:href="wlkp-20170930.xsd#DescriptionOfBusinessAndBasisOfPresentationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DescriptionOfBusinessAndBasisOfPresentationPolicies" xlink:href="wlkp-20170930.xsd#DescriptionOfBusinessAndBasisOfPresentationPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnit" xlink:href="wlkp-20170930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnit" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitBasicAndDilutedIncomePerLimitedPartnerUnitDetails" xlink:href="wlkp-20170930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnitBasicAndDilutedIncomePerLimitedPartnerUnitDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitDistributionsDeclaredDetails" xlink:href="wlkp-20170930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnitDistributionsDeclaredDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitIncomeInExcessOfDistributionDetails" xlink:href="wlkp-20170930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnitIncomeInExcessOfDistributionDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitTables" xlink:href="wlkp-20170930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnitTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DocumentAndEntityInformation" xlink:href="wlkp-20170930.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/Equity" xlink:href="wlkp-20170930.xsd#Equity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/EquityDetails" xlink:href="wlkp-20170930.xsd#EquityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/FairValueMeasurements" xlink:href="wlkp-20170930.xsd#FairValueMeasurements" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/FairValueMeasurementsSummaryOfAssetsAndLiabilitiesAccountedAtFairValueOnRecurringAndNonrecurringBasisDetails" xlink:href="wlkp-20170930.xsd#FairValueMeasurementsSummaryOfAssetsAndLiabilitiesAccountedAtFairValueOnRecurringAndNonrecurringBasisDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/FairValueMeasurementsSummaryOfCarryingAndFairValuesOfLongTermDebtDetails" xlink:href="wlkp-20170930.xsd#FairValueMeasurementsSummaryOfCarryingAndFairValuesOfLongTermDebtDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/FairValueMeasurementsTables" xlink:href="wlkp-20170930.xsd#FairValueMeasurementsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/Inventories" xlink:href="wlkp-20170930.xsd#Inventories" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/InventoriesDetails" xlink:href="wlkp-20170930.xsd#InventoriesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/InventoriesTables" xlink:href="wlkp-20170930.xsd#InventoriesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/LongTermDebtPayableToWestlake" xlink:href="wlkp-20170930.xsd#LongTermDebtPayableToWestlake" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/LongTermDebtPayableToWestlakeDetails" xlink:href="wlkp-20170930.xsd#LongTermDebtPayableToWestlakeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/LongTermDebtPayableToWestlakeTables" xlink:href="wlkp-20170930.xsd#LongTermDebtPayableToWestlakeTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/MajorCustomerAndConcentrationRisk" xlink:href="wlkp-20170930.xsd#MajorCustomerAndConcentrationRisk" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/MajorCustomerAndConcentrationRiskDetails" xlink:href="wlkp-20170930.xsd#MajorCustomerAndConcentrationRiskDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/OtherAssets" xlink:href="wlkp-20170930.xsd#OtherAssets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/OtherAssetsDetails" xlink:href="wlkp-20170930.xsd#OtherAssetsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/PropertyPlantAndEquipment" xlink:href="wlkp-20170930.xsd#PropertyPlantAndEquipment" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/PropertyPlantAndEquipmentDetail" xlink:href="wlkp-20170930.xsd#PropertyPlantAndEquipmentDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactions" xlink:href="wlkp-20170930.xsd#RelatedPartyTransactions" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsAccountsReceivableFromAndAccountsPayableToRelatedPartiesDetails" xlink:href="wlkp-20170930.xsd#RelatedPartyTransactionsAccountsReceivableFromAndAccountsPayableToRelatedPartiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsCostOfSalesFromRelatedPartiesDetails" xlink:href="wlkp-20170930.xsd#RelatedPartyTransactionsCostOfSalesFromRelatedPartiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsDebtPayableToRelatedPartiesDetails" xlink:href="wlkp-20170930.xsd#RelatedPartyTransactionsDebtPayableToRelatedPartiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsGeneralDetails" xlink:href="wlkp-20170930.xsd#RelatedPartyTransactionsGeneralDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsGoodsAndServicesFromRelatedPartiesThatHaveBeenCapitalizedDetails" xlink:href="wlkp-20170930.xsd#RelatedPartyTransactionsGoodsAndServicesFromRelatedPartiesThatHaveBeenCapitalizedDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsSalesToRelatedPartiesDetails" xlink:href="wlkp-20170930.xsd#RelatedPartyTransactionsSalesToRelatedPartiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsServicesFromRelatedPartiesIncludedInSgaExpensesDetails" xlink:href="wlkp-20170930.xsd#RelatedPartyTransactionsServicesFromRelatedPartiesIncludedInSgaExpensesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsSiteLeaseAgreementsDetails" xlink:href="wlkp-20170930.xsd#RelatedPartyTransactionsSiteLeaseAgreementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsTables" xlink:href="wlkp-20170930.xsd#RelatedPartyTransactionsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/SubsequentEvents" xlink:href="wlkp-20170930.xsd#SubsequentEvents" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/SubsequentEventsDetails" xlink:href="wlkp-20170930.xsd#SubsequentEventsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/SupplementalInformation" xlink:href="wlkp-20170930.xsd#SupplementalInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/SupplementalInformationDetails" xlink:href="wlkp-20170930.xsd#SupplementalInformationDetails" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/AccountsReceivableThirdParties" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/AccountsReceivableThirdPartiesAccountsReceivablethirdPartiesScheduleOfAccountsReceivableDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/AccountsReceivableThirdPartiesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/AccumulatedOtherComprehensiveIncomeLoss" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/AccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_64D13CC32DCC5C06000C5C8FE8AD78E9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_AB2C7D4292B49A383EBA5C8FE8ACAF55" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_64D13CC32DCC5C06000C5C8FE8AD78E9" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_AB2C7D4292B49A383EBA5C8FE8ACAF55" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_D3D21245A1E74D80090F5C8FE8AC8D8D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_AB2C7D4292B49A383EBA5C8FE8ACAF55" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_D3D21245A1E74D80090F5C8FE8AC8D8D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_CE01A51FFD68D070E6B15C8FE8AC1618_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_D3D21245A1E74D80090F5C8FE8AC8D8D" xlink:to="loc_us-gaap_EquityComponentDomain_CE01A51FFD68D070E6B15C8FE8AC1618_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_CE01A51FFD68D070E6B15C8FE8AC1618" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_D3D21245A1E74D80090F5C8FE8AC8D8D" xlink:to="loc_us-gaap_EquityComponentDomain_CE01A51FFD68D070E6B15C8FE8AC1618" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember" xlink:label="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_C14D673CE2AE3B23270B5C8FE8AD1D49" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_CE01A51FFD68D070E6B15C8FE8AC1618" xlink:to="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_C14D673CE2AE3B23270B5C8FE8AD1D49" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_DF453C7471F331A9E2445C8FE8AD1CBE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_64D13CC32DCC5C06000C5C8FE8AD78E9" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_DF453C7471F331A9E2445C8FE8AD1CBE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_BFCDB440E47E9165A8F15C8FE8AD5F37" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_64D13CC32DCC5C06000C5C8FE8AD78E9" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_BFCDB440E47E9165A8F15C8FE8AD5F37" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_018897638DBB9BCDE72C5C8FE8ADD6AE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_64D13CC32DCC5C06000C5C8FE8AD78E9" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_018897638DBB9BCDE72C5C8FE8ADD6AE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/AccumulatedOtherComprehensiveIncomeLossTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/CommitmentsAndContingenciesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingenciesLineItems" xlink:label="loc_us-gaap_LossContingenciesLineItems_ED93C55F2810F8B15CCAE61D36FBA625" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingenciesTable" xlink:label="loc_us-gaap_LossContingenciesTable_9342891E1A5AE6276FACE61D36FB9CB9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_ED93C55F2810F8B15CCAE61D36FBA625" xlink:to="loc_us-gaap_LossContingenciesTable_9342891E1A5AE6276FACE61D36FB9CB9" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LitigationStatusAxis" xlink:label="loc_us-gaap_LitigationStatusAxis_1DC7B8D2A76C525BAB03E61D36FBBC64" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_9342891E1A5AE6276FACE61D36FB9CB9" xlink:to="loc_us-gaap_LitigationStatusAxis_1DC7B8D2A76C525BAB03E61D36FBBC64" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LitigationStatusDomain" xlink:label="loc_us-gaap_LitigationStatusDomain_85FF994E9D45BC997647E61D36FB49B1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_1DC7B8D2A76C525BAB03E61D36FBBC64" xlink:to="loc_us-gaap_LitigationStatusDomain_85FF994E9D45BC997647E61D36FB49B1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LitigationStatusDomain" xlink:label="loc_us-gaap_LitigationStatusDomain_85FF994E9D45BC997647E61D36FB49B1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_1DC7B8D2A76C525BAB03E61D36FBBC64" xlink:to="loc_us-gaap_LitigationStatusDomain_85FF994E9D45BC997647E61D36FB49B1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PendingLitigationMember" xlink:label="loc_us-gaap_PendingLitigationMember_36701D041D10E6BEB3A1E61D36FBB110" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_85FF994E9D45BC997647E61D36FB49B1" xlink:to="loc_us-gaap_PendingLitigationMember_36701D041D10E6BEB3A1E61D36FBB110" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SettledLitigationMember" xlink:label="loc_us-gaap_SettledLitigationMember_4CFE4D5FA47DEBBE9406E61D36FB4065" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_85FF994E9D45BC997647E61D36FB49B1" xlink:to="loc_us-gaap_SettledLitigationMember_4CFE4D5FA47DEBBE9406E61D36FB4065" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_01C9D30FA586BA9FA49AE61D36FBE8A5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_9342891E1A5AE6276FACE61D36FB9CB9" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_01C9D30FA586BA9FA49AE61D36FBE8A5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingencyNatureDomain" xlink:label="loc_us-gaap_LossContingencyNatureDomain_D7897E2648D5D6680B69E61D36FBC329_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_01C9D30FA586BA9FA49AE61D36FBE8A5" xlink:to="loc_us-gaap_LossContingencyNatureDomain_D7897E2648D5D6680B69E61D36FBC329_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingencyNatureDomain" xlink:label="loc_us-gaap_LossContingencyNatureDomain_D7897E2648D5D6680B69E61D36FBC329" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_01C9D30FA586BA9FA49AE61D36FBE8A5" xlink:to="loc_us-gaap_LossContingencyNatureDomain_D7897E2648D5D6680B69E61D36FBC329" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_UnfavorableRegulatoryActionMember" xlink:label="loc_us-gaap_UnfavorableRegulatoryActionMember_F4E4EAE1632EDBAFEE66E61D36FB7E5E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_D7897E2648D5D6680B69E61D36FBC329" xlink:to="loc_us-gaap_UnfavorableRegulatoryActionMember_F4E4EAE1632EDBAFEE66E61D36FB7E5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingencyEstimateOfPossibleLoss" xlink:label="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_F20856DEA7F683C36981E61D36FB9DD6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ED93C55F2810F8B15CCAE61D36FBA625" xlink:to="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_F20856DEA7F683C36981E61D36FB9DD6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingencyClaimsSettledNumber" xlink:label="loc_us-gaap_LossContingencyClaimsSettledNumber_C6B0EC94CA76747862C0E61D36FB9AC0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ED93C55F2810F8B15CCAE61D36FBA625" xlink:to="loc_us-gaap_LossContingencyClaimsSettledNumber_C6B0EC94CA76747862C0E61D36FB9AC0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_5CC26835DA9C8C8505ECE62050088D71" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_ED93C55F2810F8B15CCAE61D36FBA625" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_5CC26835DA9C8C8505ECE62050088D71" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_7BD6D5613BCFCE61B9D75C8C3F130E5B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_64EB7915F4A299D77F2D5C8C3F114E23" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_7BD6D5613BCFCE61B9D75C8C3F130E5B" xlink:to="loc_us-gaap_StatementTable_64EB7915F4A299D77F2D5C8C3F114E23" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_65072177AAECCE32F4635C8C3F112240" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_64EB7915F4A299D77F2D5C8C3F114E23" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_65072177AAECCE32F4635C8C3F112240" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_58C23939B0B7BC08CA095C8C3F114123_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_65072177AAECCE32F4635C8C3F112240" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_58C23939B0B7BC08CA095C8C3F114123_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_58C23939B0B7BC08CA095C8C3F114123" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_65072177AAECCE32F4635C8C3F112240" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_58C23939B0B7BC08CA095C8C3F114123" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_A38B36A31A1102A5FA2A5C8C3F11A5C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_58C23939B0B7BC08CA095C8C3F114123" xlink:to="loc_us-gaap_LimitedPartnerMember_A38B36A31A1102A5FA2A5C8C3F11A5C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GeneralPartnerMember" xlink:label="loc_us-gaap_GeneralPartnerMember_B64E4C261711419D7AA35C8C3F1275F7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_58C23939B0B7BC08CA095C8C3F114123" xlink:to="loc_us-gaap_GeneralPartnerMember_B64E4C261711419D7AA35C8C3F1275F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_691ADA76A6F5C904B9755C8C3F125B92" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_64EB7915F4A299D77F2D5C8C3F114E23" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_691ADA76A6F5C904B9755C8C3F125B92" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_6D9AE66A4258EA9A87485C8C3F127FB3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_691ADA76A6F5C904B9755C8C3F125B92" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_6D9AE66A4258EA9A87485C8C3F127FB3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_6D9AE66A4258EA9A87485C8C3F127FB3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_691ADA76A6F5C904B9755C8C3F125B92" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_6D9AE66A4258EA9A87485C8C3F127FB3" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_A361CB034E477C496D075C8C3F122959" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_6D9AE66A4258EA9A87485C8C3F127FB3" xlink:to="loc_wlkp_CommonUnitsMember_A361CB034E477C496D075C8C3F122959" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_210CEA513CF22B2F66085C8C3F13EE00" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_6D9AE66A4258EA9A87485C8C3F127FB3" xlink:to="loc_wlkp_SubordinatedUnitsMember_210CEA513CF22B2F66085C8C3F13EE00" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_291F4270860F263D1F0D5C8C3F131ED9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_64EB7915F4A299D77F2D5C8C3F114E23" xlink:to="loc_us-gaap_CounterpartyNameAxis_291F4270860F263D1F0D5C8C3F131ED9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_1851A2775C1C4EEDC2F25C8C3F131440_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_291F4270860F263D1F0D5C8C3F131ED9" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_1851A2775C1C4EEDC2F25C8C3F131440_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_1851A2775C1C4EEDC2F25C8C3F131440" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_291F4270860F263D1F0D5C8C3F131ED9" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_1851A2775C1C4EEDC2F25C8C3F131440" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_UnidentifiedThirdPartiesMember" xlink:label="loc_wlkp_UnidentifiedThirdPartiesMember_232CE65BD1689E2C331A5C8C3F135C35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_1851A2775C1C4EEDC2F25C8C3F131440" xlink:to="loc_wlkp_UnidentifiedThirdPartiesMember_232CE65BD1689E2C331A5C8C3F135C35" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_212FE3674A7145F91DB15C8C3F13E699" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_1851A2775C1C4EEDC2F25C8C3F131440" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_212FE3674A7145F91DB15C8C3F13E699" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="loc_us-gaap_AssetsAbstract_F3D66B3FCCF157E99D915C8C3F132984" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7BD6D5613BCFCE61B9D75C8C3F130E5B" xlink:to="loc_us-gaap_AssetsAbstract_F3D66B3FCCF157E99D915C8C3F132984" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="loc_us-gaap_AssetsCurrentAbstract_4F2D41DCBACB7DBD77EF5C8C3F1530F0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_F3D66B3FCCF157E99D915C8C3F132984" xlink:to="loc_us-gaap_AssetsCurrentAbstract_4F2D41DCBACB7DBD77EF5C8C3F1530F0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_DCD3AD508FEF241639735C8C3F15D578" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_4F2D41DCBACB7DBD77EF5C8C3F1530F0" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_DCD3AD508FEF241639735C8C3F15D578" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent" xlink:label="loc_wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent_4D1E2A0DCFF851B1541E5C8C3F15131B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_4F2D41DCBACB7DBD77EF5C8C3F1530F0" xlink:to="loc_wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent_4D1E2A0DCFF851B1541E5C8C3F15131B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsReceivableRelatedPartiesCurrent" xlink:label="loc_us-gaap_AccountsReceivableRelatedPartiesCurrent_58FF07E1D0B3D0789F515C8C3F153599" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_4F2D41DCBACB7DBD77EF5C8C3F1530F0" xlink:to="loc_us-gaap_AccountsReceivableRelatedPartiesCurrent_58FF07E1D0B3D0789F515C8C3F153599" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReceivablesNetCurrent" xlink:label="loc_us-gaap_ReceivablesNetCurrent_44E02196C08C9AD0B6D65C8C3F1591A1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_4F2D41DCBACB7DBD77EF5C8C3F1530F0" xlink:to="loc_us-gaap_ReceivablesNetCurrent_44E02196C08C9AD0B6D65C8C3F1591A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InventoryNet" xlink:label="loc_us-gaap_InventoryNet_56421F84A32785D0BBCE5C8C3F15AC5E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_4F2D41DCBACB7DBD77EF5C8C3F1530F0" xlink:to="loc_us-gaap_InventoryNet_56421F84A32785D0BBCE5C8C3F15AC5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_841D3066069B635BF7D75C8C3F15998A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_4F2D41DCBACB7DBD77EF5C8C3F1530F0" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_841D3066069B635BF7D75C8C3F15998A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaap_AssetsCurrent_9A1CCF516DBF9A28C2115C8C3F156C10" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_4F2D41DCBACB7DBD77EF5C8C3F1530F0" xlink:to="loc_us-gaap_AssetsCurrent_9A1CCF516DBF9A28C2115C8C3F156C10" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_94C7C6723633376BB0FF5C8C3F157105" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_F3D66B3FCCF157E99D915C8C3F132984" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_94C7C6723633376BB0FF5C8C3F157105" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherAssetsAbstract" xlink:label="loc_us-gaap_OtherAssetsAbstract_A4B53996CF9A296C8A775C8C3F15FAD9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_F3D66B3FCCF157E99D915C8C3F132984" xlink:to="loc_us-gaap_OtherAssetsAbstract_A4B53996CF9A296C8A775C8C3F15FAD9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_94CF0770C54F38F0DF5D5C8C3F15A3AF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_A4B53996CF9A296C8A775C8C3F15FAD9" xlink:to="loc_us-gaap_Goodwill_94CF0770C54F38F0DF5D5C8C3F15A3AF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredCostsAndOtherAssets" xlink:label="loc_us-gaap_DeferredCostsAndOtherAssets_A631B7B9712FAA2B26F85C8C3F152762" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_A4B53996CF9A296C8A775C8C3F15FAD9" xlink:to="loc_us-gaap_DeferredCostsAndOtherAssets_A631B7B9712FAA2B26F85C8C3F152762" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_E2803E2A35F678C23DE35C8C3F156A78" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_A4B53996CF9A296C8A775C8C3F15FAD9" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_E2803E2A35F678C23DE35C8C3F156A78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaap_Assets_CA844E15D7A606CA80195C8C3F164A71" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_F3D66B3FCCF157E99D915C8C3F132984" xlink:to="loc_us-gaap_Assets_CA844E15D7A606CA80195C8C3F164A71" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_79407836B95226DC98955C8C3F166CE5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7BD6D5613BCFCE61B9D75C8C3F130E5B" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_79407836B95226DC98955C8C3F166CE5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_41CC2F2DFB475D86E0B55C8C3F16401F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_79407836B95226DC98955C8C3F166CE5" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_41CC2F2DFB475D86E0B55C8C3F16401F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsPayableRelatedPartiesCurrent" xlink:label="loc_us-gaap_AccountsPayableRelatedPartiesCurrent_07A473C9B4986C6C31545C8C3F16901A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_41CC2F2DFB475D86E0B55C8C3F16401F" xlink:to="loc_us-gaap_AccountsPayableRelatedPartiesCurrent_07A473C9B4986C6C31545C8C3F16901A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="loc_us-gaap_AccountsPayableCurrent_E216606365ADD907C8085C8C3F16FC8E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_41CC2F2DFB475D86E0B55C8C3F16401F" xlink:to="loc_us-gaap_AccountsPayableCurrent_E216606365ADD907C8085C8C3F16FC8E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_02E1BF713E28383BC09B5C8C3F16EFDA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_41CC2F2DFB475D86E0B55C8C3F16401F" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_02E1BF713E28383BC09B5C8C3F16EFDA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaap_LiabilitiesCurrent_4F49FFDB00ABC8145CD45C8C3F165BFB" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_41CC2F2DFB475D86E0B55C8C3F16401F" xlink:to="loc_us-gaap_LiabilitiesCurrent_4F49FFDB00ABC8145CD45C8C3F165BFB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DueToRelatedPartiesNoncurrent" xlink:label="loc_us-gaap_DueToRelatedPartiesNoncurrent_0BA82CA3551DE56FE58E5C8C3F16FA05" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_79407836B95226DC98955C8C3F166CE5" xlink:to="loc_us-gaap_DueToRelatedPartiesNoncurrent_0BA82CA3551DE56FE58E5C8C3F16FA05" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredTaxLiabilitiesNoncurrent" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesNoncurrent_30AFBFD9CC4F4720FF9E5C8C3F16B8B3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_79407836B95226DC98955C8C3F166CE5" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesNoncurrent_30AFBFD9CC4F4720FF9E5C8C3F16B8B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_EFBEFE57504AA030A3C65C8C3F1645FC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_79407836B95226DC98955C8C3F166CE5" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_EFBEFE57504AA030A3C65C8C3F1645FC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Liabilities" xlink:label="loc_us-gaap_Liabilities_2F19686504433BA174015C8C3F16D9CC" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_79407836B95226DC98955C8C3F166CE5" xlink:to="loc_us-gaap_Liabilities_2F19686504433BA174015C8C3F16D9CC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="loc_us-gaap_CommitmentsAndContingencies_181E73EDFA25A76C1FB45C8C3F16207E" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_79407836B95226DC98955C8C3F166CE5" xlink:to="loc_us-gaap_CommitmentsAndContingencies_181E73EDFA25A76C1FB45C8C3F16207E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="loc_us-gaap_StockholdersEquityAbstract_0D0BA79F1EAD9A18CEF65C8C3F166C5F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7BD6D5613BCFCE61B9D75C8C3F130E5B" xlink:to="loc_us-gaap_StockholdersEquityAbstract_0D0BA79F1EAD9A18CEF65C8C3F166C5F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccount" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccount_43E21C1979F1950D9BF15C8C3F162609" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_0D0BA79F1EAD9A18CEF65C8C3F166C5F" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccount_43E21C1979F1950D9BF15C8C3F162609" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GeneralPartnersCapitalAccount" xlink:label="loc_us-gaap_GeneralPartnersCapitalAccount_C0DD9DC97CB9F4AA72E55C8C3F173E74" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_0D0BA79F1EAD9A18CEF65C8C3F166C5F" xlink:to="loc_us-gaap_GeneralPartnersCapitalAccount_C0DD9DC97CB9F4AA72E55C8C3F173E74" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_B5A63BE404669A5C8DA65C8C3F175D9D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_0D0BA79F1EAD9A18CEF65C8C3F166C5F" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_B5A63BE404669A5C8DA65C8C3F175D9D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnersCapital" xlink:label="loc_us-gaap_PartnersCapital_57DDF7F18E52525497BB5C8C3F1753D9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_0D0BA79F1EAD9A18CEF65C8C3F166C5F" xlink:to="loc_us-gaap_PartnersCapital_57DDF7F18E52525497BB5C8C3F1753D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinorityInterestInLimitedPartnerships" xlink:label="loc_us-gaap_MinorityInterestInLimitedPartnerships_756D685076AED171BA815C8C3F179F48" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_0D0BA79F1EAD9A18CEF65C8C3F166C5F" xlink:to="loc_us-gaap_MinorityInterestInLimitedPartnerships_756D685076AED171BA815C8C3F179F48" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_9FDD87E5269A93DC97A35C8C3F170054" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_0D0BA79F1EAD9A18CEF65C8C3F166C5F" xlink:to="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_9FDD87E5269A93DC97A35C8C3F170054" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_3D5FB0E133B9783EEAD45C8C3F17CE68" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_0D0BA79F1EAD9A18CEF65C8C3F166C5F" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_3D5FB0E133B9783EEAD45C8C3F17CE68" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_93D977A43F357B302AC3E61B824259CB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_0C4B243FAEEE0698E5B5E61B82422A35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_93D977A43F357B302AC3E61B824259CB" xlink:to="loc_us-gaap_StatementTable_0C4B243FAEEE0698E5B5E61B82422A35" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_7941BECD26DA9C78F9CCE61B824201EC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_0C4B243FAEEE0698E5B5E61B82422A35" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_7941BECD26DA9C78F9CCE61B824201EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9EE058D287B98D8C2E00E61B82428198_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_7941BECD26DA9C78F9CCE61B824201EC" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9EE058D287B98D8C2E00E61B82428198_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9EE058D287B98D8C2E00E61B82428198" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_7941BECD26DA9C78F9CCE61B824201EC" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9EE058D287B98D8C2E00E61B82428198" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_623667E899AE3FC98739E61B82425C3A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9EE058D287B98D8C2E00E61B82428198" xlink:to="loc_wlkp_CommonUnitsMember_623667E899AE3FC98739E61B82425C3A" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_9CB0219D9F75E0218781E61B8242E06B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9EE058D287B98D8C2E00E61B82428198" xlink:to="loc_wlkp_SubordinatedUnitsMember_9CB0219D9F75E0218781E61B8242E06B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_E45B92CF48254BDEEFE9E61B82422E64" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_0C4B243FAEEE0698E5B5E61B82422A35" xlink:to="loc_us-gaap_CounterpartyNameAxis_E45B92CF48254BDEEFE9E61B82422E64" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_7D21805E73EE3135B436E61B82426991_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_E45B92CF48254BDEEFE9E61B82422E64" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_7D21805E73EE3135B436E61B82426991_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_7D21805E73EE3135B436E61B82426991" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_E45B92CF48254BDEEFE9E61B82422E64" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_7D21805E73EE3135B436E61B82426991" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_UnidentifiedThirdPartiesMember" xlink:label="loc_wlkp_UnidentifiedThirdPartiesMember_E569E90FD14AAAF256B6E61B82423B71" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_7D21805E73EE3135B436E61B82426991" xlink:to="loc_wlkp_UnidentifiedThirdPartiesMember_E569E90FD14AAAF256B6E61B82423B71" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_D590587C21C9AD08D258E61B82429AD9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_7D21805E73EE3135B436E61B82426991" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_D590587C21C9AD08D258E61B82429AD9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsIssued" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsIssued_6BDAEED48C537BC3FBF5E61B82427420" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_93D977A43F357B302AC3E61B824259CB" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsIssued_6BDAEED48C537BC3FBF5E61B82427420" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_CA21C20F0AFDF49A05A8E61B82429B67" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_93D977A43F357B302AC3E61B824259CB" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_CA21C20F0AFDF49A05A8E61B82429B67" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/ConsolidatedStatementsOfCashFlows" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/ConsolidatedStatementsOfChangesInEquity" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_DFA7A476DF5A5DC82EA35C8F0CBE04B7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_F26FD80E8DEB0921CE915C8F0CBD9904" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_DFA7A476DF5A5DC82EA35C8F0CBE04B7" xlink:to="loc_us-gaap_StatementTable_F26FD80E8DEB0921CE915C8F0CBD9904" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_3F1DC3E5E0507F97BD035C8F0CBDBACE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_F26FD80E8DEB0921CE915C8F0CBD9904" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_3F1DC3E5E0507F97BD035C8F0CBDBACE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F8A9D788012D60BB12B65C8F0CBD0707_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_3F1DC3E5E0507F97BD035C8F0CBDBACE" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F8A9D788012D60BB12B65C8F0CBD0707_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F8A9D788012D60BB12B65C8F0CBD0707" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_3F1DC3E5E0507F97BD035C8F0CBDBACE" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F8A9D788012D60BB12B65C8F0CBD0707" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_ED69E1A3EC2857C1285C5C8F0CBD1195" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F8A9D788012D60BB12B65C8F0CBD0707" xlink:to="loc_wlkp_CommonUnitsMember_ED69E1A3EC2857C1285C5C8F0CBD1195" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_4F8242DA192775A934F95C8F0CBDAEEB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F8A9D788012D60BB12B65C8F0CBD0707" xlink:to="loc_wlkp_SubordinatedUnitsMember_4F8242DA192775A934F95C8F0CBDAEEB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_65C773A345010D61D7445C8F0CBD516B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_F26FD80E8DEB0921CE915C8F0CBD9904" xlink:to="loc_us-gaap_CounterpartyNameAxis_65C773A345010D61D7445C8F0CBD516B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_38867BBCC83575919ED45C8F0CBD2820_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_65C773A345010D61D7445C8F0CBD516B" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_38867BBCC83575919ED45C8F0CBD2820_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_38867BBCC83575919ED45C8F0CBD2820" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_65C773A345010D61D7445C8F0CBD516B" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_38867BBCC83575919ED45C8F0CBD2820" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_UnidentifiedThirdPartiesMember" xlink:label="loc_wlkp_UnidentifiedThirdPartiesMember_467660F41DF8C708B0585C8F0CBD0830" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_38867BBCC83575919ED45C8F0CBD2820" xlink:to="loc_wlkp_UnidentifiedThirdPartiesMember_467660F41DF8C708B0585C8F0CBD0830" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_5FBCA25B61212C2D7C815C8F0CBD0329" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_38867BBCC83575919ED45C8F0CBD2820" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_5FBCA25B61212C2D7C815C8F0CBD0329" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_C1353031FD5DC800F00F5C8F0CBDA183" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_F26FD80E8DEB0921CE915C8F0CBD9904" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_C1353031FD5DC800F00F5C8F0CBDA183" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_B2F35AA466D36F42E9375C8F0CBDF713_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_C1353031FD5DC800F00F5C8F0CBDA183" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_B2F35AA466D36F42E9375C8F0CBDF713_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_B2F35AA466D36F42E9375C8F0CBDF713" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_C1353031FD5DC800F00F5C8F0CBDA183" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_B2F35AA466D36F42E9375C8F0CBDF713" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_197BC36B9F0FEF7646735C8F0CBDB6DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_B2F35AA466D36F42E9375C8F0CBDF713" xlink:to="loc_us-gaap_LimitedPartnerMember_197BC36B9F0FEF7646735C8F0CBDB6DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GeneralPartnerMember" xlink:label="loc_us-gaap_GeneralPartnerMember_1EADAF8008B564636E645C8F0CBEFC5E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_B2F35AA466D36F42E9375C8F0CBDF713" xlink:to="loc_us-gaap_GeneralPartnerMember_1EADAF8008B564636E645C8F0CBEFC5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_3A8A4CA5BDE4C43568725C8F0CBE19C9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_F26FD80E8DEB0921CE915C8F0CBD9904" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_3A8A4CA5BDE4C43568725C8F0CBE19C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_D6EFAC737E14D2D9A6B35C8F0CBE36FA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_3A8A4CA5BDE4C43568725C8F0CBE19C9" xlink:to="loc_us-gaap_EquityComponentDomain_D6EFAC737E14D2D9A6B35C8F0CBE36FA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_D6EFAC737E14D2D9A6B35C8F0CBE36FA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_3A8A4CA5BDE4C43568725C8F0CBE19C9" xlink:to="loc_us-gaap_EquityComponentDomain_D6EFAC737E14D2D9A6B35C8F0CBE36FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_0F20554EF6774462147B5C8F0CBEAF44" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_D6EFAC737E14D2D9A6B35C8F0CBE36FA" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_0F20554EF6774462147B5C8F0CBEAF44" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="loc_us-gaap_NoncontrollingInterestMember_7955CCBE542CAD2EF21E5C8F0CBE7E85" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_D6EFAC737E14D2D9A6B35C8F0CBE36FA" xlink:to="loc_us-gaap_NoncontrollingInterestMember_7955CCBE542CAD2EF21E5C8F0CBE7E85" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_13F069B4CCB842DE8AE25C8F0CBE15E2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_DFA7A476DF5A5DC82EA35C8F0CBE04B7" xlink:to="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_13F069B4CCB842DE8AE25C8F0CBE15E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_04D3EFEE978707BFC4BB5C8F0CBEB8D2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_DFA7A476DF5A5DC82EA35C8F0CBE04B7" xlink:to="loc_us-gaap_ProfitLoss_04D3EFEE978707BFC4BB5C8F0CBEB8D2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax_B733C492D3CAD9502D225C8F0CBE44E2" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_DFA7A476DF5A5DC82EA35C8F0CBE04B7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax_B733C492D3CAD9502D225C8F0CBE44E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity" xlink:label="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_70CAA117566DEEC704BD5C8F0CBE0D20" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_DFA7A476DF5A5DC82EA35C8F0CBE04B7" xlink:to="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_70CAA117566DEEC704BD5C8F0CBE0D20" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ConversionofUnitsAmount" xlink:label="loc_wlkp_ConversionofUnitsAmount_9AFD8D0B6B5114C70B465C8F0CBEB8CB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_DFA7A476DF5A5DC82EA35C8F0CBE04B7" xlink:to="loc_wlkp_ConversionofUnitsAmount_9AFD8D0B6B5114C70B465C8F0CBEB8CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountDistributionAmount" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountDistributionAmount_7E3DE83FB623EF2FD6A65C8F0CBE6E71" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_DFA7A476DF5A5DC82EA35C8F0CBE04B7" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountDistributionAmount_7E3DE83FB623EF2FD6A65C8F0CBE6E71" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_F9DA28CEA89ADC721D495C8F0CBE6873" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_DFA7A476DF5A5DC82EA35C8F0CBE04B7" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_F9DA28CEA89ADC721D495C8F0CBE6873" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/ConsolidatedStatementsOfComprehensiveIncome" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/ConsolidatedStatementsOfOperations" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_778704A739445686A2277457182D3DD0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_StatementTable_778704A739445686A2277457182D3DD0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2B892BA701F371F9779D7457182E6ABD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_778704A739445686A2277457182D3DD0" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2B892BA701F371F9779D7457182E6ABD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_4CD318EF07D04D5F3BC27457182E1FA2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2B892BA701F371F9779D7457182E6ABD" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_4CD318EF07D04D5F3BC27457182E1FA2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_4CD318EF07D04D5F3BC27457182E1FA2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2B892BA701F371F9779D7457182E6ABD" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_4CD318EF07D04D5F3BC27457182E1FA2" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_FCFD26322260DE6F09AA7457182EC0DF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_4CD318EF07D04D5F3BC27457182E1FA2" xlink:to="loc_wlkp_CommonUnitsMember_FCFD26322260DE6F09AA7457182EC0DF" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_DF65897D6A382ACCC5AB7457182EE1A6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_4CD318EF07D04D5F3BC27457182E1FA2" xlink:to="loc_wlkp_SubordinatedUnitsMember_DF65897D6A382ACCC5AB7457182EE1A6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_9861A36ED1428F3084F37457182E663E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_778704A739445686A2277457182D3DD0" xlink:to="loc_us-gaap_CounterpartyNameAxis_9861A36ED1428F3084F37457182E663E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6D878404C5A318D29EB97457182E53FD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_9861A36ED1428F3084F37457182E663E" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6D878404C5A318D29EB97457182E53FD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6D878404C5A318D29EB97457182E53FD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_9861A36ED1428F3084F37457182E663E" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6D878404C5A318D29EB97457182E53FD" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_UnidentifiedThirdPartiesMember" xlink:label="loc_wlkp_UnidentifiedThirdPartiesMember_490A958DB4E8656AB2D57457182EA3FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6D878404C5A318D29EB97457182E53FD" xlink:to="loc_wlkp_UnidentifiedThirdPartiesMember_490A958DB4E8656AB2D57457182EA3FB" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_850AD80B958AEAC721EB7457182EE42D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6D878404C5A318D29EB97457182E53FD" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_850AD80B958AEAC721EB7457182EE42D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueFromRelatedParties" xlink:label="loc_us-gaap_RevenueFromRelatedParties_57729E5EFE8FD75E21A57457182F0A46" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_RevenueFromRelatedParties_57729E5EFE8FD75E21A57457182F0A46" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherSalesRevenueNet" xlink:label="loc_us-gaap_OtherSalesRevenueNet_3366421B05FC87F8C1E87457182FB71F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_OtherSalesRevenueNet_3366421B05FC87F8C1E87457182FB71F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SalesRevenueNet" xlink:label="loc_us-gaap_SalesRevenueNet_19080EF2AF36765EACD67457182F9E61" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_SalesRevenueNet_19080EF2AF36765EACD67457182F9E61" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CostOfGoodsSold" xlink:label="loc_us-gaap_CostOfGoodsSold_709C0ECA68EB8D56DB287457182F9737" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_CostOfGoodsSold_709C0ECA68EB8D56DB287457182F9737" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GrossProfit" xlink:label="loc_us-gaap_GrossProfit_7A51E0FAD8F496CE35017457182FD7D5" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_GrossProfit_7A51E0FAD8F496CE35017457182FD7D5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_6B7D6616F59F77E7F8437457182F2216" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_6B7D6616F59F77E7F8437457182F2216" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_FA4B8C79CA1F171F54E3745718302652" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_OperatingIncomeLoss_FA4B8C79CA1F171F54E3745718302652" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NonoperatingIncomeExpenseAbstract" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_0287BA2F2A63F210095274571830A272" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_0287BA2F2A63F210095274571830A272" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpenseRelatedParty" xlink:label="loc_us-gaap_InterestExpenseRelatedParty_B04DD8DE1085AFE8929C745718300002" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_0287BA2F2A63F210095274571830A272" xlink:to="loc_us-gaap_InterestExpenseRelatedParty_B04DD8DE1085AFE8929C745718300002" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_DE00F39644EBB869A80D745718300C44" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_0287BA2F2A63F210095274571830A272" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_DE00F39644EBB869A80D745718300C44" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_8103983BBCB3BEAEDEF9745718300FD8" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_8103983BBCB3BEAEDEF9745718300FD8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_C68B715B72971CE0AD2C74571830E62E" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_C68B715B72971CE0AD2C74571830E62E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_A95786BADDA3C2642CD7745718300929" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_ProfitLoss_A95786BADDA3C2642CD7745718300929" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_C727A6031E95CCE53E1874571830847B" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_C727A6031E95CCE53E1874571830847B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_AD7CF338136DE361CAC47457183038B8" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_NetIncomeLoss_AD7CF338136DE361CAC47457183038B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_413741406027272627B174571830AB2A" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_413741406027272627B174571830AB2A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDiluted_E7707A946B2170EDB6CE74571831C526" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_413741406027272627B174571830AB2A" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDiluted_E7707A946B2170EDB6CE74571831C526" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_1DF10A65D05B38452BA97457183190CA" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_1DF10A65D05B38452BA97457183190CA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:label="loc_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_B5E96ADCB53EFD9EC19D745718313552" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_1DF10A65D05B38452BA97457183190CA" xlink:to="loc_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_B5E96ADCB53EFD9EC19D745718313552" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionMadeToLimitedPartnerDistributionsPaidPerUnit" xlink:label="loc_us-gaap_DistributionMadeToLimitedPartnerDistributionsPaidPerUnit_B4BF1B8FEAE0322780FA745718311D13" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1C482CE1E64904D9202C7457182F73C9" xlink:to="loc_us-gaap_DistributionMadeToLimitedPartnerDistributionsPaidPerUnit_B4BF1B8FEAE0322780FA745718311D13" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/DerivativeInstruments" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/DerivativeInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeLineItems" xlink:label="loc_us-gaap_DerivativeLineItems_F4D90BEA3930683DEEFE319DBE5E52F5" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeTable" xlink:label="loc_us-gaap_DerivativeTable_6F6844AA329436BD0BB2319DBE5E7E2A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_F4D90BEA3930683DEEFE319DBE5E52F5" xlink:to="loc_us-gaap_DerivativeTable_6F6844AA329436BD0BB2319DBE5E7E2A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_EB6EFDBD854A4FC394B2319DBE5E4335" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_6F6844AA329436BD0BB2319DBE5E7E2A" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_EB6EFDBD854A4FC394B2319DBE5E4335" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_8D631457EE69AC8532F2319DBE5EA456_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_EB6EFDBD854A4FC394B2319DBE5E4335" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_8D631457EE69AC8532F2319DBE5EA456_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_8D631457EE69AC8532F2319DBE5EA456" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_EB6EFDBD854A4FC394B2319DBE5E4335" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_8D631457EE69AC8532F2319DBE5EA456" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestRateContractMember" xlink:label="loc_us-gaap_InterestRateContractMember_352762C168E6F069A2C9319DBE5ED242" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_8D631457EE69AC8532F2319DBE5EA456" xlink:to="loc_us-gaap_InterestRateContractMember_352762C168E6F069A2C9319DBE5ED242" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_HedgingDesignationAxis" xlink:label="loc_us-gaap_HedgingDesignationAxis_1D063A033E5BA2592FB3319DBE5E33C0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_6F6844AA329436BD0BB2319DBE5E7E2A" xlink:to="loc_us-gaap_HedgingDesignationAxis_1D063A033E5BA2592FB3319DBE5E33C0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_E6953845BE31606B4D15319DBE5EE76D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_1D063A033E5BA2592FB3319DBE5E33C0" xlink:to="loc_us-gaap_HedgingDesignationDomain_E6953845BE31606B4D15319DBE5EE76D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_E6953845BE31606B4D15319DBE5EE76D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_1D063A033E5BA2592FB3319DBE5E33C0" xlink:to="loc_us-gaap_HedgingDesignationDomain_E6953845BE31606B4D15319DBE5EE76D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_825F0E438249DEF2B360319DBE5E4A5C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_6F6844AA329436BD0BB2319DBE5E7E2A" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_825F0E438249DEF2B360319DBE5E4A5C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_729B42D256A6CFDC7BDC319DBE5E9C61_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_825F0E438249DEF2B360319DBE5E4A5C" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_729B42D256A6CFDC7BDC319DBE5E9C61_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_729B42D256A6CFDC7BDC319DBE5E9C61" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_825F0E438249DEF2B360319DBE5E4A5C" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_729B42D256A6CFDC7BDC319DBE5E9C61" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpenseMember" xlink:label="loc_us-gaap_InterestExpenseMember_6B436FCA1211DD708853319DBE5EB7C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_729B42D256A6CFDC7BDC319DBE5E9C61" xlink:to="loc_us-gaap_InterestExpenseMember_6B436FCA1211DD708853319DBE5EB7C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C629BA2B5163130C8FE9319DBE5E2906" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_6F6844AA329436BD0BB2319DBE5E7E2A" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C629BA2B5163130C8FE9319DBE5E2906" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_6ECEB75648F1716520DD319DBE5E7AD4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C629BA2B5163130C8FE9319DBE5E2906" xlink:to="loc_us-gaap_HedgingRelationshipDomain_6ECEB75648F1716520DD319DBE5E7AD4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_6ECEB75648F1716520DD319DBE5E7AD4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C629BA2B5163130C8FE9319DBE5E2906" xlink:to="loc_us-gaap_HedgingRelationshipDomain_6ECEB75648F1716520DD319DBE5E7AD4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashFlowHedgingMember" xlink:label="loc_us-gaap_CashFlowHedgingMember_D50FA0B3EE7F8CD8A14F319DBE5E0D96" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_6ECEB75648F1716520DD319DBE5E7AD4" xlink:to="loc_us-gaap_CashFlowHedgingMember_D50FA0B3EE7F8CD8A14F319DBE5E0D96" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_DFDE13612C874260C35D319DBE5E0A12" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_6F6844AA329436BD0BB2319DBE5E7E2A" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_DFDE13612C874260C35D319DBE5E0A12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_6BAE0CD8A1C72F0797AF319DBE5E7766_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_DFDE13612C874260C35D319DBE5E0A12" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_6BAE0CD8A1C72F0797AF319DBE5E7766_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_6BAE0CD8A1C72F0797AF319DBE5E7766" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_DFDE13612C874260C35D319DBE5E0A12" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_6BAE0CD8A1C72F0797AF319DBE5E7766" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherAssetsMember" xlink:label="loc_us-gaap_OtherAssetsMember_C350079D6CB6A6A1AA25319DBE5E2E39" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_6BAE0CD8A1C72F0797AF319DBE5E7766" xlink:to="loc_us-gaap_OtherAssetsMember_C350079D6CB6A6A1AA25319DBE5E2E39" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion" xlink:label="loc_us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_D894B4C10FF3AA13AA6D31B80BA65EC6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_F4D90BEA3930683DEEFE319DBE5E52F5" xlink:to="loc_us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_D894B4C10FF3AA13AA6D31B80BA65EC6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestRateDerivativeAssetsAtFairValue" xlink:label="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_9FB981BFE109904482F0319DBE5E963D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_F4D90BEA3930683DEEFE319DBE5E52F5" xlink:to="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_9FB981BFE109904482F0319DBE5E963D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeInstrumentsLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion" xlink:label="loc_us-gaap_DerivativeInstrumentsLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_23B8A577F9BA031C5DA9319DBE5EE9D0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_F4D90BEA3930683DEEFE319DBE5E52F5" xlink:to="loc_us-gaap_DerivativeInstrumentsLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_23B8A577F9BA031C5DA9319DBE5EE9D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet_47532F2818445F458093319DBE5E8203" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_F4D90BEA3930683DEEFE319DBE5E52F5" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet_47532F2818445F458093319DBE5E8203" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet_1F917398CE71234BBDED319DBE5EB94A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_F4D90BEA3930683DEEFE319DBE5E52F5" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet_1F917398CE71234BBDED319DBE5EB94A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/DerivativeInstrumentsIneffectivePortionDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/DerivativeInstrumentsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/DescriptionOfBusinessAndBasisOfPresentation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/DescriptionOfBusinessAndBasisOfPresentationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountLineItems" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_29C89D31F792782F98D35E9D6818E425" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable" xlink:label="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_D52A96761DDDA3CC126E5E9D68158510" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_29C89D31F792782F98D35E9D6818E425" xlink:to="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_D52A96761DDDA3CC126E5E9D68158510" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_78FD573C4CB5EFC9ECDF5E9D6816068D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_D52A96761DDDA3CC126E5E9D68158510" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_78FD573C4CB5EFC9ECDF5E9D6816068D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_08DA6597C136BE8C7F1F5E9D6816BDED_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_78FD573C4CB5EFC9ECDF5E9D6816068D" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_08DA6597C136BE8C7F1F5E9D6816BDED_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_08DA6597C136BE8C7F1F5E9D6816BDED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_78FD573C4CB5EFC9ECDF5E9D6816068D" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_08DA6597C136BE8C7F1F5E9D6816BDED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_569A7F6C433DE17C00E45E9D68167820" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_08DA6597C136BE8C7F1F5E9D6816BDED" xlink:to="loc_us-gaap_LimitedPartnerMember_569A7F6C433DE17C00E45E9D68167820" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_F6B49E99343FEE1AA5345E9D681773A2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_D52A96761DDDA3CC126E5E9D68158510" xlink:to="loc_dei_LegalEntityAxis_F6B49E99343FEE1AA5345E9D681773A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_14733F0AEC91AB22EE6D5E9D68170F13_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_F6B49E99343FEE1AA5345E9D681773A2" xlink:to="loc_dei_EntityDomain_14733F0AEC91AB22EE6D5E9D68170F13_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_14733F0AEC91AB22EE6D5E9D68170F13" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_F6B49E99343FEE1AA5345E9D681773A2" xlink:to="loc_dei_EntityDomain_14733F0AEC91AB22EE6D5E9D68170F13" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_1C1C41D16F55D87308035E9D68173372" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_14733F0AEC91AB22EE6D5E9D68170F13" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_1C1C41D16F55D87308035E9D68173372" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_WestlakeChemicalOpCoLPMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoLPMember_606AAA9C9885CD8289175E9D681767BD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_14733F0AEC91AB22EE6D5E9D68170F13" xlink:to="loc_wlkp_WestlakeChemicalOpCoLPMember_606AAA9C9885CD8289175E9D681767BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_1416F3BECEB65C2410405E9D6817DFF1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_D52A96761DDDA3CC126E5E9D68158510" xlink:to="loc_us-gaap_CounterpartyNameAxis_1416F3BECEB65C2410405E9D6817DFF1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AB550A81E9FB72044C345E9D68184686_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_1416F3BECEB65C2410405E9D6817DFF1" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AB550A81E9FB72044C345E9D68184686_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AB550A81E9FB72044C345E9D68184686" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_1416F3BECEB65C2410405E9D6817DFF1" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AB550A81E9FB72044C345E9D68184686" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_7A7206742520590609FC5E9D68186156" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AB550A81E9FB72044C345E9D68184686" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_7A7206742520590609FC5E9D68186156" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_WestlakeChemicalOpCoLPMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoLPMember_7A08F714577524C0BAE25E9D6818CC72" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AB550A81E9FB72044C345E9D68184686" xlink:to="loc_wlkp_WestlakeChemicalOpCoLPMember_7A08F714577524C0BAE25E9D6818CC72" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_WestlakeChemicalOpCoGPLLCMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoGPLLCMember_92C5786B8C184D802E985E9D681845AE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AB550A81E9FB72044C345E9D68184686" xlink:to="loc_wlkp_WestlakeChemicalOpCoGPLLCMember_92C5786B8C184D802E985E9D681845AE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F70344BEF5EE9B456FA95E9D6818AB4C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_D52A96761DDDA3CC126E5E9D68158510" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F70344BEF5EE9B456FA95E9D6818AB4C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_4652D5D892EE851C87AD5E9D6818D01E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F70344BEF5EE9B456FA95E9D6818AB4C" xlink:to="loc_us-gaap_RelatedPartyDomain_4652D5D892EE851C87AD5E9D6818D01E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_4652D5D892EE851C87AD5E9D6818D01E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F70344BEF5EE9B456FA95E9D6818AB4C" xlink:to="loc_us-gaap_RelatedPartyDomain_4652D5D892EE851C87AD5E9D6818D01E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:label="loc_us-gaap_AffiliatedEntityMember_EEF69E8F1EC8F8FDFE8E5E9D68186434" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_4652D5D892EE851C87AD5E9D6818D01E" xlink:to="loc_us-gaap_AffiliatedEntityMember_EEF69E8F1EC8F8FDFE8E5E9D68186434" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_WestlakeChemicalOpCoLPMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoLPMember_B7D64964E3F0D9D738525E9D6818FC02" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_4652D5D892EE851C87AD5E9D6818D01E" xlink:to="loc_wlkp_WestlakeChemicalOpCoLPMember_B7D64964E3F0D9D738525E9D6818FC02" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedLiabilityCompanyMember" xlink:label="loc_us-gaap_LimitedLiabilityCompanyMember_7FD97871A028A3AF43A45E9D6818DD09" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_4652D5D892EE851C87AD5E9D6818D01E" xlink:to="loc_us-gaap_LimitedLiabilityCompanyMember_7FD97871A028A3AF43A45E9D6818DD09" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorityOwnedSubsidiaryUnconsolidatedMember" xlink:label="loc_us-gaap_MajorityOwnedSubsidiaryUnconsolidatedMember_A3C3922D8B7C016A03D35E9D68181DDD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_4652D5D892EE851C87AD5E9D6818D01E" xlink:to="loc_us-gaap_MajorityOwnedSubsidiaryUnconsolidatedMember_A3C3922D8B7C016A03D35E9D68181DDD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering" xlink:label="loc_us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering_3F3139AFFB3C0CD75A8C5E9D68189E68" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_29C89D31F792782F98D35E9D6818E425" xlink:to="loc_us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering_3F3139AFFB3C0CD75A8C5E9D68189E68" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit" xlink:label="loc_wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit_7CCBA4F120BCE3B3BF265E9D68188F72" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_29C89D31F792782F98D35E9D6818E425" xlink:to="loc_wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit_7CCBA4F120BCE3B3BF265E9D68188F72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity" xlink:label="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_09D10B6F11D569AB9EA75E9D6818700B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_29C89D31F792782F98D35E9D6818E425" xlink:to="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_09D10B6F11D569AB9EA75E9D6818700B" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity" xlink:label="loc_wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity_5EA0523B486C0FE96CB15E9D68186338" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_29C89D31F792782F98D35E9D6818E425" xlink:to="loc_wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity_5EA0523B486C0FE96CB15E9D68186338" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest" xlink:label="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest_E3CF0F818A34A9D2C2CB5E9D68198A4A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_29C89D31F792782F98D35E9D6818E425" xlink:to="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest_E3CF0F818A34A9D2C2CB5E9D68198A4A" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_LimitedLiabilityCompanyLLCorLimitedPartnershipLPMembersorLimitedPartnersAdditionalOwnershipInterest" xlink:label="loc_wlkp_LimitedLiabilityCompanyLLCorLimitedPartnershipLPMembersorLimitedPartnersAdditionalOwnershipInterest_CED2B0E64DB2A96E0A335E9D68194756" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_29C89D31F792782F98D35E9D6818E425" xlink:to="loc_wlkp_LimitedLiabilityCompanyLLCorLimitedPartnershipLPMembersorLimitedPartnersAdditionalOwnershipInterest_CED2B0E64DB2A96E0A335E9D68194756" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireLimitedPartnershipInterests" xlink:label="loc_us-gaap_PaymentsToAcquireLimitedPartnershipInterests_2DDB2547313D764551805E9D6819A3EA" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_29C89D31F792782F98D35E9D6818E425" xlink:to="loc_us-gaap_PaymentsToAcquireLimitedPartnershipInterests_2DDB2547313D764551805E9D6819A3EA" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_NumberofProductionFacilities" xlink:label="loc_wlkp_NumberofProductionFacilities_76BEB918AB4F074652FD5E9D6819386F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_29C89D31F792782F98D35E9D6818E425" xlink:to="loc_wlkp_NumberofProductionFacilities_76BEB918AB4F074652FD5E9D6819386F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/DescriptionOfBusinessAndBasisOfPresentationPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnit" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitBasicAndDilutedIncomePerLimitedPartnerUnitDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountLineItems" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_C312772BD5C61B4C147DE61B8232B535" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable" xlink:label="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_5D0E0E37D9192A03ED5FE61B8232096B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_C312772BD5C61B4C147DE61B8232B535" xlink:to="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_5D0E0E37D9192A03ED5FE61B8232096B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_C5EB0CDED691FF4FFFA8E61B8232DEEB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_5D0E0E37D9192A03ED5FE61B8232096B" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_C5EB0CDED691FF4FFFA8E61B8232DEEB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_9BEAF0FAE3222017EDFCE61B8232F4C1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_C5EB0CDED691FF4FFFA8E61B8232DEEB" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_9BEAF0FAE3222017EDFCE61B8232F4C1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_9BEAF0FAE3222017EDFCE61B8232F4C1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_C5EB0CDED691FF4FFFA8E61B8232DEEB" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_9BEAF0FAE3222017EDFCE61B8232F4C1" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_74266E952D430A88E228E61B8232888B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_9BEAF0FAE3222017EDFCE61B8232F4C1" xlink:to="loc_wlkp_IDRHoldersMember_74266E952D430A88E228E61B8232888B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_425313D0E33AB6D04355E61B82323657" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_5D0E0E37D9192A03ED5FE61B8232096B" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_425313D0E33AB6D04355E61B82323657" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_D0D081C9BB0F9602F048E61B82329D02_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_425313D0E33AB6D04355E61B82323657" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_D0D081C9BB0F9602F048E61B82329D02_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_D0D081C9BB0F9602F048E61B82329D02" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_425313D0E33AB6D04355E61B82323657" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_D0D081C9BB0F9602F048E61B82329D02" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_598751B1571CC5FD0D72E61B823292D5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_D0D081C9BB0F9602F048E61B82329D02" xlink:to="loc_wlkp_CommonUnitsMember_598751B1571CC5FD0D72E61B823292D5" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_39BABB07468798D24F66E61B8232C72E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_D0D081C9BB0F9602F048E61B82329D02" xlink:to="loc_wlkp_SubordinatedUnitsMember_39BABB07468798D24F66E61B8232C72E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributedEarnings" xlink:label="loc_us-gaap_DistributedEarnings_A9AB0F05290F1C3D8C47E61B8232A7E3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_C312772BD5C61B4C147DE61B8232B535" xlink:to="loc_us-gaap_DistributedEarnings_A9AB0F05290F1C3D8C47E61B8232A7E3" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IncentiveDistributionSubsequentDistributionAmount" xlink:label="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_58136249C6EB4C7818DBE61B82329C68" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_C312772BD5C61B4C147DE61B8232B535" xlink:to="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_58136249C6EB4C7818DBE61B82329C68" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_UndistributedEarnings" xlink:label="loc_us-gaap_UndistributedEarnings_3B0223D1B92C03290658E61B8232D6F8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_C312772BD5C61B4C147DE61B8232B535" xlink:to="loc_us-gaap_UndistributedEarnings_3B0223D1B92C03290658E61B8232D6F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_C24A472325D9B6FA5933E61B8232F775" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_C312772BD5C61B4C147DE61B8232B535" xlink:to="loc_us-gaap_NetIncomeLoss_C24A472325D9B6FA5933E61B8232F775" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_B4B1200D88D46273E675E61B82326822" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_C312772BD5C61B4C147DE61B8232B535" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_B4B1200D88D46273E675E61B82326822" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:label="loc_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_F27B4AE49EA3CE43F539E61B8232F2EA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_B4B1200D88D46273E675E61B82326822" xlink:to="loc_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_F27B4AE49EA3CE43F539E61B8232F2EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_23729AD3C151CD8F80FBE61B8232BD62" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_C312772BD5C61B4C147DE61B8232B535" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_23729AD3C151CD8F80FBE61B8232BD62" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDiluted_6B8B8DB0AC2CBCB6B694E61B8232ED8A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_23729AD3C151CD8F80FBE61B8232BD62" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDiluted_6B8B8DB0AC2CBCB6B694E61B8232ED8A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitDistributionsDeclaredDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionMadeToLimitedPartnerLineItems" xlink:label="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionsMadeToLimitedPartnerTable" xlink:label="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_739441DF535E63C31CA85C8FE95D60E7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_739441DF535E63C31CA85C8FE95D60E7" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis" xlink:label="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_D9B85DAC1B7B09AFD95C5C8FE95D81A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_739441DF535E63C31CA85C8FE95D60E7" xlink:to="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_D9B85DAC1B7B09AFD95C5C8FE95D81A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_26169486B311D31867DE5C8FE95DB1A1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_D9B85DAC1B7B09AFD95C5C8FE95D81A3" xlink:to="loc_us-gaap_DistributionTypeDomain_26169486B311D31867DE5C8FE95DB1A1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_26169486B311D31867DE5C8FE95DB1A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_D9B85DAC1B7B09AFD95C5C8FE95D81A3" xlink:to="loc_us-gaap_DistributionTypeDomain_26169486B311D31867DE5C8FE95DB1A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashDistributionMember" xlink:label="loc_us-gaap_CashDistributionMember_254B6B459041C323E6D15C8FE95D48DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionTypeDomain_26169486B311D31867DE5C8FE95DB1A1" xlink:to="loc_us-gaap_CashDistributionMember_254B6B459041C323E6D15C8FE95D48DC" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CashDistributionTrancheOneMember" xlink:label="loc_wlkp_CashDistributionTrancheOneMember_AD28D313B0A8760C85DE5C8FE95D0757" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashDistributionMember_254B6B459041C323E6D15C8FE95D48DC" xlink:to="loc_wlkp_CashDistributionTrancheOneMember_AD28D313B0A8760C85DE5C8FE95D0757" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CashDistributionTrancheTwoMember" xlink:label="loc_wlkp_CashDistributionTrancheTwoMember_3C5D5D0477FBD63445745C8FE95D7B80" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashDistributionMember_254B6B459041C323E6D15C8FE95D48DC" xlink:to="loc_wlkp_CashDistributionTrancheTwoMember_3C5D5D0477FBD63445745C8FE95D7B80" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CashDistributionTrancheThreeMember" xlink:label="loc_wlkp_CashDistributionTrancheThreeMember_0594A0D59FBC1DBCC9B35C8FE95DB8A0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashDistributionMember_254B6B459041C323E6D15C8FE95D48DC" xlink:to="loc_wlkp_CashDistributionTrancheThreeMember_0594A0D59FBC1DBCC9B35C8FE95DB8A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_F0AE47EBDE2C6E2AE96D5C8FE95DF0F0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_739441DF535E63C31CA85C8FE95D60E7" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_F0AE47EBDE2C6E2AE96D5C8FE95DF0F0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_7C218A623BB879ADE1C35C8FE95EBAE6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_F0AE47EBDE2C6E2AE96D5C8FE95DF0F0" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_7C218A623BB879ADE1C35C8FE95EBAE6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_7C218A623BB879ADE1C35C8FE95EBAE6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_F0AE47EBDE2C6E2AE96D5C8FE95DF0F0" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_7C218A623BB879ADE1C35C8FE95EBAE6" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_B032AFAA471C38EE75035C8FE95EF155" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_7C218A623BB879ADE1C35C8FE95EBAE6" xlink:to="loc_wlkp_CommonUnitsMember_B032AFAA471C38EE75035C8FE95EF155" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_00B4E2DDA9936903732C5C8FE95EF978" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_7C218A623BB879ADE1C35C8FE95EBAE6" xlink:to="loc_wlkp_SubordinatedUnitsMember_00B4E2DDA9936903732C5C8FE95EF978" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CommonAndSubordinatedUnitsMember" xlink:label="loc_wlkp_CommonAndSubordinatedUnitsMember_0F5FC478F0B3229896B65C8FE95E68BA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_7C218A623BB879ADE1C35C8FE95EBAE6" xlink:to="loc_wlkp_CommonAndSubordinatedUnitsMember_0F5FC478F0B3229896B65C8FE95E68BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_2CF3066437F5536AAADB5C8FE95E8A64" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_739441DF535E63C31CA85C8FE95D60E7" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_2CF3066437F5536AAADB5C8FE95E8A64" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_C82380178F5FA6F5AF7B5C8FE95EAD39_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_2CF3066437F5536AAADB5C8FE95E8A64" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_C82380178F5FA6F5AF7B5C8FE95EAD39_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_C82380178F5FA6F5AF7B5C8FE95EAD39" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_2CF3066437F5536AAADB5C8FE95E8A64" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_C82380178F5FA6F5AF7B5C8FE95EAD39" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_4EE41C154736223F18105C8FE95E8EE0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_C82380178F5FA6F5AF7B5C8FE95EAD39" xlink:to="loc_wlkp_IDRHoldersMember_4EE41C154736223F18105C8FE95E8EE0" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_UnitHoldersMember" xlink:label="loc_wlkp_UnitHoldersMember_FA984A81F2D3D24C07E65C8FE95E22F2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_C82380178F5FA6F5AF7B5C8FE95EAD39" xlink:to="loc_wlkp_UnitHoldersMember_FA984A81F2D3D24C07E65C8FE95E22F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_9A117B7815E903D68D6C5CCE64851F42" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_739441DF535E63C31CA85C8FE95D60E7" xlink:to="loc_us-gaap_CounterpartyNameAxis_9A117B7815E903D68D6C5CCE64851F42" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_C30CF1FD12C33A99EE845CCE649E333F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_9A117B7815E903D68D6C5CCE64851F42" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_C30CF1FD12C33A99EE845CCE649E333F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_C30CF1FD12C33A99EE845CCE649E333F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_9A117B7815E903D68D6C5CCE64851F42" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_C30CF1FD12C33A99EE845CCE649E333F" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_E46A910220D8D63424535CCE6637F723" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_C30CF1FD12C33A99EE845CCE649E333F" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_E46A910220D8D63424535CCE6637F723" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_1FBCCE81374D179F206A5C8FE95E337A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_739441DF535E63C31CA85C8FE95D60E7" xlink:to="loc_us-gaap_RangeAxis_1FBCCE81374D179F206A5C8FE95E337A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_2EB76FC63A005135E75C5C8FE95ED626_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_1FBCCE81374D179F206A5C8FE95E337A" xlink:to="loc_us-gaap_RangeMember_2EB76FC63A005135E75C5C8FE95ED626_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_2EB76FC63A005135E75C5C8FE95ED626" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_1FBCCE81374D179F206A5C8FE95E337A" xlink:to="loc_us-gaap_RangeMember_2EB76FC63A005135E75C5C8FE95ED626" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_EB1B0FF6AB76F11DAE415C8FE95EF78A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_2EB76FC63A005135E75C5C8FE95ED626" xlink:to="loc_us-gaap_MinimumMember_EB1B0FF6AB76F11DAE415C8FE95EF78A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_C0DD1C10EA02D15207C95C8FE95EF305" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_2EB76FC63A005135E75C5C8FE95ED626" xlink:to="loc_us-gaap_MaximumMember_C0DD1C10EA02D15207C95C8FE95EF305" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_40F69CC430D9A016F75D5C8FE95E337C" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_739441DF535E63C31CA85C8FE95D60E7" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_40F69CC430D9A016F75D5C8FE95E337C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_C22E14E27201DC7A63765C8FE95E5E0F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_40F69CC430D9A016F75D5C8FE95E337C" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_C22E14E27201DC7A63765C8FE95E5E0F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_C22E14E27201DC7A63765C8FE95E5E0F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_40F69CC430D9A016F75D5C8FE95E337C" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_C22E14E27201DC7A63765C8FE95E5E0F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_8EFCA84C3B1386A0277B5C8FE95E22F9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_C22E14E27201DC7A63765C8FE95E5E0F" xlink:to="loc_us-gaap_SubsequentEventMember_8EFCA84C3B1386A0277B5C8FE95E22F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit" xlink:label="loc_us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit_A16F0F897E57B8A74B6C5C8FE95F1E84" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit_A16F0F897E57B8A74B6C5C8FE95F1E84" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionDistributionPerYear" xlink:label="loc_us-gaap_IncentiveDistributionDistributionPerYear_CEFDF77B79CE73D6233A5C8FE95F016E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_us-gaap_IncentiveDistributionDistributionPerYear_CEFDF77B79CE73D6233A5C8FE95F016E" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_MinimumQuarterlyDistributionPerUnit" xlink:label="loc_wlkp_MinimumQuarterlyDistributionPerUnit_68282227DCB0457885B65C8FE95F584A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_wlkp_MinimumQuarterlyDistributionPerUnit_68282227DCB0457885B65C8FE95F584A" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IncentiveDistributionMarginalPercentageInterestinDistributions" xlink:label="loc_wlkp_IncentiveDistributionMarginalPercentageInterestinDistributions_A6D12552CC62BD2D8B285C8FE95F3B3E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_wlkp_IncentiveDistributionMarginalPercentageInterestinDistributions_A6D12552CC62BD2D8B285C8FE95F3B3E" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IncentiveDistributionRightsTargetDistributionPerUnitRequiringMarginalPercentageDistributiontoIDRHolders" xlink:label="loc_wlkp_IncentiveDistributionRightsTargetDistributionPerUnitRequiringMarginalPercentageDistributiontoIDRHolders_C82D9771EE1FCD0526675C8FE95FF0C6" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_wlkp_IncentiveDistributionRightsTargetDistributionPerUnitRequiringMarginalPercentageDistributiontoIDRHolders_C82D9771EE1FCD0526675C8FE95FF0C6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_C249B1FCAAA1F03CD6715C8FE95FBCB3" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_us-gaap_NetIncomeLoss_C249B1FCAAA1F03CD6715C8FE95FBCB3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributedEarnings" xlink:label="loc_us-gaap_DistributedEarnings_6711B8DCDE09B6238DA95C8FE95FF6AE" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_us-gaap_DistributedEarnings_6711B8DCDE09B6238DA95C8FE95FF6AE" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IncentiveDistributionSubsequentDistributionAmount" xlink:label="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_381145A322B958AF1FEB5C8FE95FB8F5" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_381145A322B958AF1FEB5C8FE95FB8F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_UndistributedEarnings" xlink:label="loc_us-gaap_UndistributedEarnings_981CF3F8302AD99C005F5C8FE95F198A" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_us-gaap_UndistributedEarnings_981CF3F8302AD99C005F5C8FE95F198A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_C9490EE5C27E6B8A842F5CCE63DD62F7" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_C9490EE5C27E6B8A842F5CCE63DD62F7" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IncentiveDistributionQuarterlyDistributionPerUnitDistributionThreshold" xlink:label="loc_wlkp_IncentiveDistributionQuarterlyDistributionPerUnitDistributionThreshold_073130581B9926FA84D95C8FE95F6EB5" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_0651D7FF8B7A633F96565C8FE95F8999" xlink:to="loc_wlkp_IncentiveDistributionQuarterlyDistributionPerUnitDistributionThreshold_073130581B9926FA84D95C8FE95F6EB5" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitIncomeInExcessOfDistributionDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_6BDBEB0F0B865A9E4EC2E61B804E6E14" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable" xlink:label="loc_us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable_5C2A16452988F3D0CF43E61B804E9342" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_6BDBEB0F0B865A9E4EC2E61B804E6E14" xlink:to="loc_us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable_5C2A16452988F3D0CF43E61B804E9342" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis" xlink:label="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_A104BA114FE1A6CB4E7BE61B804E7D90" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable_5C2A16452988F3D0CF43E61B804E9342" xlink:to="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_A104BA114FE1A6CB4E7BE61B804E7D90" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_AEF94765355F40479A25E61B804E0D09_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_A104BA114FE1A6CB4E7BE61B804E7D90" xlink:to="loc_us-gaap_DistributionTypeDomain_AEF94765355F40479A25E61B804E0D09_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_AEF94765355F40479A25E61B804E0D09" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_A104BA114FE1A6CB4E7BE61B804E7D90" xlink:to="loc_us-gaap_DistributionTypeDomain_AEF94765355F40479A25E61B804E0D09" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashDistributionMember" xlink:label="loc_us-gaap_CashDistributionMember_5346120ABCD303929BBFE61B804E52B0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionTypeDomain_AEF94765355F40479A25E61B804E0D09" xlink:to="loc_us-gaap_CashDistributionMember_5346120ABCD303929BBFE61B804E52B0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_0ED4A0B1FF9D58FCC525E61B804E754F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable_5C2A16452988F3D0CF43E61B804E9342" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_0ED4A0B1FF9D58FCC525E61B804E754F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B1A56BAC04851E3A9711E61B804E4E10_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_0ED4A0B1FF9D58FCC525E61B804E754F" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B1A56BAC04851E3A9711E61B804E4E10_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B1A56BAC04851E3A9711E61B804E4E10" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_0ED4A0B1FF9D58FCC525E61B804E754F" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B1A56BAC04851E3A9711E61B804E4E10" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_FA631F8B53E0C009ACF9E61B804E4B3C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B1A56BAC04851E3A9711E61B804E4E10" xlink:to="loc_wlkp_CommonUnitsMember_FA631F8B53E0C009ACF9E61B804E4B3C" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_7C0259B3EFB22C947A14E61B804E0491" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B1A56BAC04851E3A9711E61B804E4E10" xlink:to="loc_wlkp_SubordinatedUnitsMember_7C0259B3EFB22C947A14E61B804E0491" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_BFADD7B167628CA5C2C4E61B804E3F99" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable_5C2A16452988F3D0CF43E61B804E9342" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_BFADD7B167628CA5C2C4E61B804E3F99" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_52CEB8E30880C12BCAD7E61B804E9C27_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_BFADD7B167628CA5C2C4E61B804E3F99" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_52CEB8E30880C12BCAD7E61B804E9C27_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_52CEB8E30880C12BCAD7E61B804E9C27" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_BFADD7B167628CA5C2C4E61B804E3F99" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_52CEB8E30880C12BCAD7E61B804E9C27" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_62788E1F4EB02F1196BDE61B804E4DEA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_52CEB8E30880C12BCAD7E61B804E9C27" xlink:to="loc_wlkp_IDRHoldersMember_62788E1F4EB02F1196BDE61B804E4DEA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_3667D5566EA394059020E61B804E286F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_6BDBEB0F0B865A9E4EC2E61B804E6E14" xlink:to="loc_us-gaap_NetIncomeLoss_3667D5566EA394059020E61B804E286F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributedEarnings" xlink:label="loc_us-gaap_DistributedEarnings_247A28B1F57FBDEA8F7DE61B804ED696" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_6BDBEB0F0B865A9E4EC2E61B804E6E14" xlink:to="loc_us-gaap_DistributedEarnings_247A28B1F57FBDEA8F7DE61B804ED696" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IncentiveDistributionSubsequentDistributionAmount" xlink:label="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_8DDFDA026ABEB9E997DEE61B804E5D28" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_6BDBEB0F0B865A9E4EC2E61B804E6E14" xlink:to="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_8DDFDA026ABEB9E997DEE61B804E5D28" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_UndistributedEarnings" xlink:label="loc_us-gaap_UndistributedEarnings_70E9BAC3414EB648A53EE61B804E133A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_6BDBEB0F0B865A9E4EC2E61B804E6E14" xlink:to="loc_us-gaap_UndistributedEarnings_70E9BAC3414EB648A53EE61B804E133A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/DocumentAndEntityInformation" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_DocumentInformationLineItems" xlink:label="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_DocumentInformationTable" xlink:label="loc_dei_DocumentInformationTable_E8E3A4743054DDFA758F96EE1A1ADC8F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_DocumentInformationTable_E8E3A4743054DDFA758F96EE1A1ADC8F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_F5FC883E229444C091B896EE1A1C6B41" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_E8E3A4743054DDFA758F96EE1A1ADC8F" xlink:to="loc_us-gaap_StatementClassOfStockAxis_F5FC883E229444C091B896EE1A1C6B41" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_7DE1FBBB3770503E201596EE1A1D950D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_F5FC883E229444C091B896EE1A1C6B41" xlink:to="loc_us-gaap_ClassOfStockDomain_7DE1FBBB3770503E201596EE1A1D950D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_7DE1FBBB3770503E201596EE1A1D950D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_F5FC883E229444C091B896EE1A1C6B41" xlink:to="loc_us-gaap_ClassOfStockDomain_7DE1FBBB3770503E201596EE1A1D950D" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_856455F4F5F323BF6CA696EE1A1DC066" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_7DE1FBBB3770503E201596EE1A1D950D" xlink:to="loc_wlkp_CommonUnitsMember_856455F4F5F323BF6CA696EE1A1DC066" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_DocumentType" xlink:label="loc_dei_DocumentType_01AF905D919404F7355596EE1A1D45F1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_DocumentType_01AF905D919404F7355596EE1A1D45F1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_AmendmentFlag" xlink:label="loc_dei_AmendmentFlag_0FCA263BC526EA66132896EE1A1D02C0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_AmendmentFlag_0FCA263BC526EA66132896EE1A1D02C0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_DocumentPeriodEndDate" xlink:label="loc_dei_DocumentPeriodEndDate_B354FCE26716E09CED6196EE1A1DFD6D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_DocumentPeriodEndDate_B354FCE26716E09CED6196EE1A1DFD6D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_DocumentFiscalYearFocus" xlink:label="loc_dei_DocumentFiscalYearFocus_B4177F7FF1BC13D83FE696EE1A1D58D3" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_DocumentFiscalYearFocus_B4177F7FF1BC13D83FE696EE1A1D58D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="loc_dei_DocumentFiscalPeriodFocus_C1F3C109F887B175715496EE1A1DD150" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_DocumentFiscalPeriodFocus_C1F3C109F887B175715496EE1A1DD150" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_TradingSymbol" xlink:label="loc_dei_TradingSymbol_BD483517DC65ADAA654A96EE1A1D208F" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_TradingSymbol_BD483517DC65ADAA654A96EE1A1D208F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityRegistrantName" xlink:label="loc_dei_EntityRegistrantName_A23C772975972FEB0E7A96EE1A1D825F" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_EntityRegistrantName_A23C772975972FEB0E7A96EE1A1D825F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityCentralIndexKey" xlink:label="loc_dei_EntityCentralIndexKey_924E3E263120DAFB004D96EE1A1DC271" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_EntityCentralIndexKey_924E3E263120DAFB004D96EE1A1DC271" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_CurrentFiscalYearEndDate" xlink:label="loc_dei_CurrentFiscalYearEndDate_CBE395DEB5CF34F0C39E96EE1A1E3C73" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_CurrentFiscalYearEndDate_CBE395DEB5CF34F0C39E96EE1A1E3C73" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityFilerCategory" xlink:label="loc_dei_EntityFilerCategory_89D09173121C2BE770F496EE1A1EE2A2" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_EntityFilerCategory_89D09173121C2BE770F496EE1A1EE2A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_05DB65C5F11B3985066F96EE1A1E46D7" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_7F67B5CEE1147359861C96EE1A1D54B2" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_05DB65C5F11B3985066F96EE1A1E46D7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/Equity" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/EquityDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_EC3DC2DBA4DAA3F19DBD5E9DC224EB9C" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_CF71C32F9FFA0228A6E15E9DC22360E6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_EC3DC2DBA4DAA3F19DBD5E9DC224EB9C" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_CF71C32F9FFA0228A6E15E9DC22360E6" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_4557CC5AB6FFEC243B3C5E9DC2234245" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_CF71C32F9FFA0228A6E15E9DC22360E6" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_4557CC5AB6FFEC243B3C5E9DC2234245" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_92FFF4040FE7B6AB95C25E9DC2233C6E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_4557CC5AB6FFEC243B3C5E9DC2234245" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_92FFF4040FE7B6AB95C25E9DC2233C6E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_92FFF4040FE7B6AB95C25E9DC2233C6E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_4557CC5AB6FFEC243B3C5E9DC2234245" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_92FFF4040FE7B6AB95C25E9DC2233C6E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_9E9DCA0793C8D7BD47925E9DC2232F30" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_92FFF4040FE7B6AB95C25E9DC2233C6E" xlink:to="loc_us-gaap_LimitedPartnerMember_9E9DCA0793C8D7BD47925E9DC2232F30" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_A36F2E04B234407BA7305E9DC223A850" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_CF71C32F9FFA0228A6E15E9DC22360E6" xlink:to="loc_us-gaap_CounterpartyNameAxis_A36F2E04B234407BA7305E9DC223A850" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_F7FE6C46B145D75872B05E9DC223C857_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_A36F2E04B234407BA7305E9DC223A850" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_F7FE6C46B145D75872B05E9DC223C857_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_F7FE6C46B145D75872B05E9DC223C857" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_A36F2E04B234407BA7305E9DC223A850" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_F7FE6C46B145D75872B05E9DC223C857" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_4BD879472F79650BC1EE5E9DC22480B3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_F7FE6C46B145D75872B05E9DC223C857" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_4BD879472F79650BC1EE5E9DC22480B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_13E49B15DB00BD29356B5E9DC224A87C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_CF71C32F9FFA0228A6E15E9DC22360E6" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_13E49B15DB00BD29356B5E9DC224A87C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BAC7DCC5B5AED618AD585E9DC224AB87_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_13E49B15DB00BD29356B5E9DC224A87C" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BAC7DCC5B5AED618AD585E9DC224AB87_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BAC7DCC5B5AED618AD585E9DC224AB87" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_13E49B15DB00BD29356B5E9DC224A87C" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BAC7DCC5B5AED618AD585E9DC224AB87" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_14BDC3510617CDE2B5D65E9DC22449E3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BAC7DCC5B5AED618AD585E9DC224AB87" xlink:to="loc_wlkp_SubordinatedUnitsMember_14BDC3510617CDE2B5D65E9DC22449E3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_4614EA98AF6F0ECCC0BE5E9DC224ED4F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_EC3DC2DBA4DAA3F19DBD5E9DC224EB9C" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_4614EA98AF6F0ECCC0BE5E9DC224ED4F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering" xlink:label="loc_us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering_3851D8357B1A7C72DCCF5E9DC224DAB3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_EC3DC2DBA4DAA3F19DBD5E9DC224EB9C" xlink:to="loc_us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering_3851D8357B1A7C72DCCF5E9DC224DAB3" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit" xlink:label="loc_wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit_FD455D672ADEDD9BD1EB5E9DC2249849" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_EC3DC2DBA4DAA3F19DBD5E9DC224EB9C" xlink:to="loc_wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit_FD455D672ADEDD9BD1EB5E9DC2249849" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity" xlink:label="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_92EB9C092DFA99D71C2D5E9DC22492DF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_EC3DC2DBA4DAA3F19DBD5E9DC224EB9C" xlink:to="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_92EB9C092DFA99D71C2D5E9DC22492DF" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity" xlink:label="loc_wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity_AADB4522212A0EB94BFB5E9DC2243DD3" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_EC3DC2DBA4DAA3F19DBD5E9DC224EB9C" xlink:to="loc_wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity_AADB4522212A0EB94BFB5E9DC2243DD3" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/FairValueMeasurements" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/FairValueMeasurementsSummaryOfAssetsAndLiabilitiesAccountedAtFairValueOnRecurringAndNonrecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_5B76A2105070BC938A41E61B808CA3A4" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_92E18F091E75B021343CE61B808C7C5E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_5B76A2105070BC938A41E61B808CA3A4" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_92E18F091E75B021343CE61B808C7C5E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6AD71784DCFE42644915E61B808C8E93" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_92E18F091E75B021343CE61B808C7C5E" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6AD71784DCFE42644915E61B808C8E93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_A09E2AAC4D31E5AC7ED9E61B808C1E1C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6AD71784DCFE42644915E61B808C8E93" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_A09E2AAC4D31E5AC7ED9E61B808C1E1C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_A09E2AAC4D31E5AC7ED9E61B808C1E1C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6AD71784DCFE42644915E61B808C8E93" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_A09E2AAC4D31E5AC7ED9E61B808C1E1C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_DCAB7823F302C964CFD2E61B808CF67F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_A09E2AAC4D31E5AC7ED9E61B808C1E1C" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_DCAB7823F302C964CFD2E61B808CF67F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_BB38EBB0568630090C67E61B808C8B48" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_92E18F091E75B021343CE61B808C7C5E" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_BB38EBB0568630090C67E61B808C8B48" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_CA44402FFD5A7C9BA66CE61B808CE1B3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_BB38EBB0568630090C67E61B808C8B48" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_CA44402FFD5A7C9BA66CE61B808CE1B3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_CA44402FFD5A7C9BA66CE61B808CE1B3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_BB38EBB0568630090C67E61B808C8B48" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_CA44402FFD5A7C9BA66CE61B808CE1B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestRateContractMember" xlink:label="loc_us-gaap_InterestRateContractMember_F903234F964A930ED40EE61B808C96F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_CA44402FFD5A7C9BA66CE61B808CE1B3" xlink:to="loc_us-gaap_InterestRateContractMember_F903234F964A930ED40EE61B808C96F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8DABA2694E518761BD20E61B808CDDD4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_92E18F091E75B021343CE61B808C7C5E" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8DABA2694E518761BD20E61B808CDDD4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_263EA10B47706D50903DE61B808C40F1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8DABA2694E518761BD20E61B808CDDD4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_263EA10B47706D50903DE61B808C40F1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_263EA10B47706D50903DE61B808C40F1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8DABA2694E518761BD20E61B808CDDD4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_263EA10B47706D50903DE61B808C40F1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_619887F1966E69462F46E61B808C8DFB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_263EA10B47706D50903DE61B808C40F1" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_619887F1966E69462F46E61B808C8DFB" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_InterestratecontracttransfersbetweenLevel1andLevel2fairvalueamount" xlink:label="loc_wlkp_InterestratecontracttransfersbetweenLevel1andLevel2fairvalueamount_C00A6DDE0418C8BE99B6E61B808CAAEA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_5B76A2105070BC938A41E61B808CA3A4" xlink:to="loc_wlkp_InterestratecontracttransfersbetweenLevel1andLevel2fairvalueamount_C00A6DDE0418C8BE99B6E61B808CAAEA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestRateDerivativeAssetsAtFairValue" xlink:label="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_458B4BAD95BC94201602E61B808C04B8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_5B76A2105070BC938A41E61B808CA3A4" xlink:to="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_458B4BAD95BC94201602E61B808C04B8" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/FairValueMeasurementsSummaryOfCarryingAndFairValuesOfLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_9C98039678E44CA27B4AE61B805DD971" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_A6E1CFB9B5A87D718E86E61B805D8B0F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_9C98039678E44CA27B4AE61B805DD971" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_A6E1CFB9B5A87D718E86E61B805D8B0F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_981D3FA4C9C10E283087E61B805D2DAA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_A6E1CFB9B5A87D718E86E61B805D8B0F" xlink:to="loc_us-gaap_DebtInstrumentAxis_981D3FA4C9C10E283087E61B805D2DAA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_CE8CEA28DF470D38E3E5E61B805D820E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_981D3FA4C9C10E283087E61B805D2DAA" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_CE8CEA28DF470D38E3E5E61B805D820E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_CE8CEA28DF470D38E3E5E61B805D820E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_981D3FA4C9C10E283087E61B805D2DAA" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_CE8CEA28DF470D38E3E5E61B805D820E" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_PromissoryNotes2013Member" xlink:label="loc_wlkp_PromissoryNotes2013Member_88E9FD7B4CAD4C9302D5E61B805D7B4E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_CE8CEA28DF470D38E3E5E61B805D820E" xlink:to="loc_wlkp_PromissoryNotes2013Member_88E9FD7B4CAD4C9302D5E61B805D7B4E" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_OpCoRevolverMember" xlink:label="loc_wlkp_OpCoRevolverMember_08BB85B90F66F6583F43E61B805D3235" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_CE8CEA28DF470D38E3E5E61B805D820E" xlink:to="loc_wlkp_OpCoRevolverMember_08BB85B90F66F6583F43E61B805D3235" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_MLPRevolverMember" xlink:label="loc_wlkp_MLPRevolverMember_A9E81A3EA4684C6FFA92E61B805D648A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_CE8CEA28DF470D38E3E5E61B805D820E" xlink:to="loc_wlkp_MLPRevolverMember_A9E81A3EA4684C6FFA92E61B805D648A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_7817DF3DA56ADBAB8E35E61B805DFBAB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_A6E1CFB9B5A87D718E86E61B805D8B0F" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_7817DF3DA56ADBAB8E35E61B805DFBAB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_843213A3DCF2FB32D50AE61B805DFA4C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_7817DF3DA56ADBAB8E35E61B805DFBAB" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_843213A3DCF2FB32D50AE61B805DFA4C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_843213A3DCF2FB32D50AE61B805DFA4C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_7817DF3DA56ADBAB8E35E61B805DFBAB" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_843213A3DCF2FB32D50AE61B805DFA4C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_C40EB176E553C3FC9AA9E61B805D6896" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_843213A3DCF2FB32D50AE61B805DFA4C" xlink:to="loc_us-gaap_SeniorNotesMember_C40EB176E553C3FC9AA9E61B805D6896" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SeniorUnsecuredRevolvingCreditFacilityMember" xlink:label="loc_wlkp_SeniorUnsecuredRevolvingCreditFacilityMember_5CE12E2DF9CE5DA498EAE61B805D3844" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_843213A3DCF2FB32D50AE61B805DFA4C" xlink:to="loc_wlkp_SeniorUnsecuredRevolvingCreditFacilityMember_5CE12E2DF9CE5DA498EAE61B805D3844" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2EE66E8A9E5D65DC0860E61B805DE154" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_A6E1CFB9B5A87D718E86E61B805D8B0F" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2EE66E8A9E5D65DC0860E61B805DE154" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1EB54548A9C5E55158EFE61B805DF303_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2EE66E8A9E5D65DC0860E61B805DE154" xlink:to="loc_us-gaap_RelatedPartyDomain_1EB54548A9C5E55158EFE61B805DF303_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1EB54548A9C5E55158EFE61B805DF303" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2EE66E8A9E5D65DC0860E61B805DE154" xlink:to="loc_us-gaap_RelatedPartyDomain_1EB54548A9C5E55158EFE61B805DF303" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_B2B6106B383C62AB2822E61B805DB135" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_1EB54548A9C5E55158EFE61B805DF303" xlink:to="loc_us-gaap_LimitedPartnerMember_B2B6106B383C62AB2822E61B805DB135" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestRateDerivativeAssetsAtFairValue" xlink:label="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_47A2049E159D648AAD22E61B805D2181" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_9C98039678E44CA27B4AE61B805DD971" xlink:to="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_47A2049E159D648AAD22E61B805D2181" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DueToRelatedPartiesNoncurrent" xlink:label="loc_us-gaap_DueToRelatedPartiesNoncurrent_5023E2148C59A59C4529E61B805D011F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_9C98039678E44CA27B4AE61B805DD971" xlink:to="loc_us-gaap_DueToRelatedPartiesNoncurrent_5023E2148C59A59C4529E61B805D011F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongTermDebtFairValue" xlink:label="loc_us-gaap_LongTermDebtFairValue_35BFE2DD9D8A581C1234E61B805D17C3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_9C98039678E44CA27B4AE61B805DD971" xlink:to="loc_us-gaap_LongTermDebtFairValue_35BFE2DD9D8A581C1234E61B805D17C3" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/FairValueMeasurementsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/Inventories" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/InventoriesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/InventoriesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/LongTermDebtPayableToWestlake" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/LongTermDebtPayableToWestlakeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_99A16F687B95E94ED3595C8FE8B835A2" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_EC790DBCBDD293AB46185C8FE8B6112C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_99A16F687B95E94ED3595C8FE8B835A2" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_EC790DBCBDD293AB46185C8FE8B6112C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8F3E763A7790D24008D95C8FE8B7620A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_EC790DBCBDD293AB46185C8FE8B6112C" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8F3E763A7790D24008D95C8FE8B7620A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_2BFFC3227DDF505ABAB65C8FE8B70276_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8F3E763A7790D24008D95C8FE8B7620A" xlink:to="loc_us-gaap_RelatedPartyDomain_2BFFC3227DDF505ABAB65C8FE8B70276_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_2BFFC3227DDF505ABAB65C8FE8B70276" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8F3E763A7790D24008D95C8FE8B7620A" xlink:to="loc_us-gaap_RelatedPartyDomain_2BFFC3227DDF505ABAB65C8FE8B70276" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_93ECF4A6DB5EF8553ABA5C8FE8B74F0F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_2BFFC3227DDF505ABAB65C8FE8B70276" xlink:to="loc_us-gaap_LimitedPartnerMember_93ECF4A6DB5EF8553ABA5C8FE8B74F0F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_507CAA5FE29088CF07DD5C8FE8B7DEEB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_EC790DBCBDD293AB46185C8FE8B6112C" xlink:to="loc_dei_LegalEntityAxis_507CAA5FE29088CF07DD5C8FE8B7DEEB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_5BCE71E8DE98C8062F475C8FE8B7A040_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_507CAA5FE29088CF07DD5C8FE8B7DEEB" xlink:to="loc_dei_EntityDomain_5BCE71E8DE98C8062F475C8FE8B7A040_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_5BCE71E8DE98C8062F475C8FE8B7A040" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_507CAA5FE29088CF07DD5C8FE8B7DEEB" xlink:to="loc_dei_EntityDomain_5BCE71E8DE98C8062F475C8FE8B7A040" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_OpCoRevolverMember" xlink:label="loc_wlkp_OpCoRevolverMember_A0CD9A3908EEA2D5161B5C8FE8B75FD0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_5BCE71E8DE98C8062F475C8FE8B7A040" xlink:to="loc_wlkp_OpCoRevolverMember_A0CD9A3908EEA2D5161B5C8FE8B75FD0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_B2D9F1D0785D6F3CD1D25C8FE8B7ECFE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_EC790DBCBDD293AB46185C8FE8B6112C" xlink:to="loc_us-gaap_DebtInstrumentAxis_B2D9F1D0785D6F3CD1D25C8FE8B7ECFE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_A600D3A02D79D949F0F05C8FE8B7A79B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_B2D9F1D0785D6F3CD1D25C8FE8B7ECFE" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_A600D3A02D79D949F0F05C8FE8B7A79B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_A600D3A02D79D949F0F05C8FE8B7A79B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_B2D9F1D0785D6F3CD1D25C8FE8B7ECFE" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_A600D3A02D79D949F0F05C8FE8B7A79B" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_PromissoryNotes2013Member" xlink:label="loc_wlkp_PromissoryNotes2013Member_FBD7972DD2827249A1A65C8FE8B74284" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_A600D3A02D79D949F0F05C8FE8B7A79B" xlink:to="loc_wlkp_PromissoryNotes2013Member_FBD7972DD2827249A1A65C8FE8B74284" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_OpCoRevolverMember" xlink:label="loc_wlkp_OpCoRevolverMember_5CCB86CC5E46CFA5D5075C8FE8B7B33E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_A600D3A02D79D949F0F05C8FE8B7A79B" xlink:to="loc_wlkp_OpCoRevolverMember_5CCB86CC5E46CFA5D5075C8FE8B7B33E" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_MLPRevolverMember" xlink:label="loc_wlkp_MLPRevolverMember_602433B9386B32A4FEA55C8FE8B73BD0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_A600D3A02D79D949F0F05C8FE8B7A79B" xlink:to="loc_wlkp_MLPRevolverMember_602433B9386B32A4FEA55C8FE8B73BD0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_1051108999243876099B5C8FE8B754AA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_EC790DBCBDD293AB46185C8FE8B6112C" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_1051108999243876099B5C8FE8B754AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4C22012C8191CB7783915C8FE8B75F00_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_1051108999243876099B5C8FE8B754AA" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4C22012C8191CB7783915C8FE8B75F00_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4C22012C8191CB7783915C8FE8B75F00" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_1051108999243876099B5C8FE8B754AA" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4C22012C8191CB7783915C8FE8B75F00" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_9DA01BD60A53DDAE249F5C8FE8B8D0D0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4C22012C8191CB7783915C8FE8B75F00" xlink:to="loc_us-gaap_SeniorNotesMember_9DA01BD60A53DDAE249F5C8FE8B8D0D0" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SeniorUnsecuredRevolvingCreditFacilityMember" xlink:label="loc_wlkp_SeniorUnsecuredRevolvingCreditFacilityMember_7152586942ACD92DF5CC5C8FE8B8434D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_4C22012C8191CB7783915C8FE8B75F00" xlink:to="loc_wlkp_SeniorUnsecuredRevolvingCreditFacilityMember_7152586942ACD92DF5CC5C8FE8B8434D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="loc_us-gaap_VariableRateAxis_CC05FC250B35AE730ACA5C8FE8B80EFB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_EC790DBCBDD293AB46185C8FE8B6112C" xlink:to="loc_us-gaap_VariableRateAxis_CC05FC250B35AE730ACA5C8FE8B80EFB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_6163D6CC236524A74D855C8FE8B8F03D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_CC05FC250B35AE730ACA5C8FE8B80EFB" xlink:to="loc_us-gaap_VariableRateDomain_6163D6CC236524A74D855C8FE8B8F03D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_6163D6CC236524A74D855C8FE8B8F03D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_CC05FC250B35AE730ACA5C8FE8B80EFB" xlink:to="loc_us-gaap_VariableRateDomain_6163D6CC236524A74D855C8FE8B8F03D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PrimeRateMember" xlink:label="loc_us-gaap_PrimeRateMember_39E6609B2491A58FDE145C8FE8B8DC51" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_6163D6CC236524A74D855C8FE8B8F03D" xlink:to="loc_us-gaap_PrimeRateMember_39E6609B2491A58FDE145C8FE8B8DC51" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_5903E0AB294A5CD2B8355C8FE8B8F79B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_6163D6CC236524A74D855C8FE8B8F03D" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_5903E0AB294A5CD2B8355C8FE8B8F79B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepaymentsOfDebt" xlink:label="loc_us-gaap_RepaymentsOfDebt_3A9D8EDFDFA14DC03D715C8FE8B80D23" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_99A16F687B95E94ED3595C8FE8B835A2" xlink:to="loc_us-gaap_RepaymentsOfDebt_3A9D8EDFDFA14DC03D715C8FE8B80D23" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DueToRelatedPartiesNoncurrent" xlink:label="loc_us-gaap_DueToRelatedPartiesNoncurrent_9D8F314DF38703F6F8EF5C8FE8B8EF63" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_99A16F687B95E94ED3595C8FE8B835A2" xlink:to="loc_us-gaap_DueToRelatedPartiesNoncurrent_9D8F314DF38703F6F8EF5C8FE8B8EF63" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtWeightedAverageInterestRate" xlink:label="loc_us-gaap_LongtermDebtWeightedAverageInterestRate_9973899158D4221072365C8FE8B8DC84" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_99A16F687B95E94ED3595C8FE8B835A2" xlink:to="loc_us-gaap_LongtermDebtWeightedAverageInterestRate_9973899158D4221072365C8FE8B8DC84" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_C33FA7B3ED5DA9D507F35C8FE8B8CAC2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_99A16F687B95E94ED3595C8FE8B835A2" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_C33FA7B3ED5DA9D507F35C8FE8B8CAC2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/LongTermDebtPayableToWestlakeTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/MajorCustomerAndConcentrationRisk" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/MajorCustomerAndConcentrationRiskDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskLineItems" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_E2C06F1A2CBB1975D7B05C8FE8851067" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTable" xlink:label="loc_us-gaap_ConcentrationRiskTable_12927A68D76837CDB3235C8FE8841E36" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_E2C06F1A2CBB1975D7B05C8FE8851067" xlink:to="loc_us-gaap_ConcentrationRiskTable_12927A68D76837CDB3235C8FE8841E36" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0A1F5394EC11A96846465C8FE885FFE1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_12927A68D76837CDB3235C8FE8841E36" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0A1F5394EC11A96846465C8FE885FFE1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_F858E181825D548351F55C8FE8852F25_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0A1F5394EC11A96846465C8FE885FFE1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_F858E181825D548351F55C8FE8852F25_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_F858E181825D548351F55C8FE8852F25" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0A1F5394EC11A96846465C8FE885FFE1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_F858E181825D548351F55C8FE8852F25" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SalesRevenueNetMember" xlink:label="loc_us-gaap_SalesRevenueNetMember_B2A628BD6A054D09F7015C8FE885D984" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_F858E181825D548351F55C8FE8852F25" xlink:to="loc_us-gaap_SalesRevenueNetMember_B2A628BD6A054D09F7015C8FE885D984" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_F77ED30080E481C0E49A5C8FE88557CD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_12927A68D76837CDB3235C8FE8841E36" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_F77ED30080E481C0E49A5C8FE88557CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_BE6D6648A36019263F005C8FE8859D59_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_F77ED30080E481C0E49A5C8FE88557CD" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_BE6D6648A36019263F005C8FE8859D59_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_BE6D6648A36019263F005C8FE8859D59" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_F77ED30080E481C0E49A5C8FE88557CD" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_BE6D6648A36019263F005C8FE8859D59" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_2263F7E60CFD845173485C8FE88561EB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_BE6D6648A36019263F005C8FE8859D59" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_2263F7E60CFD845173485C8FE88561EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorCustomersAxis" xlink:label="loc_us-gaap_MajorCustomersAxis_D67642B6BED1214D97B45C8FE8850F47" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_12927A68D76837CDB3235C8FE8841E36" xlink:to="loc_us-gaap_MajorCustomersAxis_D67642B6BED1214D97B45C8FE8850F47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_1D0634F4E1DDC8F505EA5C8FE885681B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorCustomersAxis_D67642B6BED1214D97B45C8FE8850F47" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_1D0634F4E1DDC8F505EA5C8FE885681B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NameOfMajorCustomerDomain" xlink:label="loc_us-gaap_NameOfMajorCustomerDomain_1D0634F4E1DDC8F505EA5C8FE885681B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorCustomersAxis_D67642B6BED1214D97B45C8FE8850F47" xlink:to="loc_us-gaap_NameOfMajorCustomerDomain_1D0634F4E1DDC8F505EA5C8FE885681B" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_98C6ACE9A11FE2D545FC5C8FE8857ACA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NameOfMajorCustomerDomain_1D0634F4E1DDC8F505EA5C8FE885681B" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_98C6ACE9A11FE2D545FC5C8FE8857ACA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_39801AB1E01BE5AE15BE5C8FE8858CFD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_12927A68D76837CDB3235C8FE8841E36" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_39801AB1E01BE5AE15BE5C8FE8858CFD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_83D17692BD60BBEB46FD5C8FE8851846_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_39801AB1E01BE5AE15BE5C8FE8858CFD" xlink:to="loc_us-gaap_RelatedPartyDomain_83D17692BD60BBEB46FD5C8FE8851846_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_83D17692BD60BBEB46FD5C8FE8851846" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_39801AB1E01BE5AE15BE5C8FE8858CFD" xlink:to="loc_us-gaap_RelatedPartyDomain_83D17692BD60BBEB46FD5C8FE8851846" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:label="loc_us-gaap_AffiliatedEntityMember_33345394377561AA2A3D5C8FE885C835" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_83D17692BD60BBEB46FD5C8FE8851846" xlink:to="loc_us-gaap_AffiliatedEntityMember_33345394377561AA2A3D5C8FE885C835" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_185F91C929CBD46753975C8FE8855A74" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_E2C06F1A2CBB1975D7B05C8FE8851067" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_185F91C929CBD46753975C8FE8855A74" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/OtherAssets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/OtherAssetsDetails" xlink:type="extended">
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_OtherAssetsLineItems" xlink:label="loc_wlkp_OtherAssetsLineItems_4B4E3A23250578B6D5175C8FE9665B8D" xlink:type="locator" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ScheduleOfOtherAssetsTable" xlink:label="loc_wlkp_ScheduleOfOtherAssetsTable_956C09DA009A84D2B1995C8FE965960C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_wlkp_OtherAssetsLineItems_4B4E3A23250578B6D5175C8FE9665B8D" xlink:to="loc_wlkp_ScheduleOfOtherAssetsTable_956C09DA009A84D2B1995C8FE965960C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_651D7526DD59F9AA45695C8FE9655658" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_wlkp_ScheduleOfOtherAssetsTable_956C09DA009A84D2B1995C8FE965960C" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_651D7526DD59F9AA45695C8FE9655658" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_46D41D1777CA189FE5E55C8FE966D42B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_651D7526DD59F9AA45695C8FE9655658" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_46D41D1777CA189FE5E55C8FE966D42B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_46D41D1777CA189FE5E55C8FE966D42B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_651D7526DD59F9AA45695C8FE9655658" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_46D41D1777CA189FE5E55C8FE966D42B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherAssetsMember" xlink:label="loc_us-gaap_OtherAssetsMember_C61379AC886A7CF0E0585C8FE9665271" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_46D41D1777CA189FE5E55C8FE966D42B" xlink:to="loc_us-gaap_OtherAssetsMember_C61379AC886A7CF0E0585C8FE9665271" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentForAmortization" xlink:label="loc_us-gaap_AdjustmentForAmortization_6517157FB2E162EEB0C05C8FE96604B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_wlkp_OtherAssetsLineItems_4B4E3A23250578B6D5175C8FE9665B8D" xlink:to="loc_us-gaap_AdjustmentForAmortization_6517157FB2E162EEB0C05C8FE96604B2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/PropertyPlantAndEquipment" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/PropertyPlantAndEquipmentDetail" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactions" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactionsAccountsReceivableFromAndAccountsPayableToRelatedPartiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_C39642D275A5C65126A35C8FE92826BB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_14CDC189DCD4D11BD3485C8FE9272256" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_C39642D275A5C65126A35C8FE92826BB" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_14CDC189DCD4D11BD3485C8FE9272256" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_E1C85AE1D93ECC5C490B5C8FE928A8A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_14CDC189DCD4D11BD3485C8FE9272256" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_E1C85AE1D93ECC5C490B5C8FE928A8A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_2E30F57581026E0309965C8FE928C564_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_E1C85AE1D93ECC5C490B5C8FE928A8A8" xlink:to="loc_us-gaap_RelatedPartyDomain_2E30F57581026E0309965C8FE928C564_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_2E30F57581026E0309965C8FE928C564" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_E1C85AE1D93ECC5C490B5C8FE928A8A8" xlink:to="loc_us-gaap_RelatedPartyDomain_2E30F57581026E0309965C8FE928C564" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:label="loc_us-gaap_AffiliatedEntityMember_0B4ED633EA183EB033505C8FE9287D30" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_2E30F57581026E0309965C8FE928C564" xlink:to="loc_us-gaap_AffiliatedEntityMember_0B4ED633EA183EB033505C8FE9287D30" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_AA97E37625541BC408475C8FE9285D53" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_14CDC189DCD4D11BD3485C8FE9272256" xlink:to="loc_us-gaap_CounterpartyNameAxis_AA97E37625541BC408475C8FE9285D53" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AE6BF38EFA545F9728355C8FE928E2BE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_AA97E37625541BC408475C8FE9285D53" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AE6BF38EFA545F9728355C8FE928E2BE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AE6BF38EFA545F9728355C8FE928E2BE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_AA97E37625541BC408475C8FE9285D53" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AE6BF38EFA545F9728355C8FE928E2BE" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_A64F0ECE501A348C94785C8FE928ED4B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_AE6BF38EFA545F9728355C8FE928E2BE" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_A64F0ECE501A348C94785C8FE928ED4B" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent" xlink:label="loc_wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent_123743A09C9CC22FE56E5CE25709FC4E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_C39642D275A5C65126A35C8FE92826BB" xlink:to="loc_wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent_123743A09C9CC22FE56E5CE25709FC4E" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_AccountsReceivableRelatedpartiesCurrentandNoncurrent" xlink:label="loc_wlkp_AccountsReceivableRelatedpartiesCurrentandNoncurrent_586BBA5E0B592CBEF8485C8FE9280C2C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_C39642D275A5C65126A35C8FE92826BB" xlink:to="loc_wlkp_AccountsReceivableRelatedpartiesCurrentandNoncurrent_586BBA5E0B592CBEF8485C8FE9280C2C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsPayableRelatedPartiesCurrent" xlink:label="loc_us-gaap_AccountsPayableRelatedPartiesCurrent_14E51C1C6F6B8EFA70855C8FE928E36D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_C39642D275A5C65126A35C8FE92826BB" xlink:to="loc_us-gaap_AccountsPayableRelatedPartiesCurrent_14E51C1C6F6B8EFA70855C8FE928E36D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactionsCostOfSalesFromRelatedPartiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_887781459BCA38C5411FE61B81A5025B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_30A89DEBC819470918A6E61B81A55FE1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_887781459BCA38C5411FE61B81A5025B" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_30A89DEBC819470918A6E61B81A55FE1" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_0548AFA6A64C4BC580A3E61B81A53A5D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_30A89DEBC819470918A6E61B81A55FE1" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_0548AFA6A64C4BC580A3E61B81A53A5D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_D28A9216B7F8BD21E421E61B81A5B0E8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_0548AFA6A64C4BC580A3E61B81A53A5D" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_D28A9216B7F8BD21E421E61B81A5B0E8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_D28A9216B7F8BD21E421E61B81A5B0E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_0548AFA6A64C4BC580A3E61B81A53A5D" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_D28A9216B7F8BD21E421E61B81A5B0E8" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_FeedstockPurchasedMember" xlink:label="loc_wlkp_FeedstockPurchasedMember_20B9EF1CAF68EB7D0CD3E61B81A549CC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_D28A9216B7F8BD21E421E61B81A5B0E8" xlink:to="loc_wlkp_FeedstockPurchasedMember_20B9EF1CAF68EB7D0CD3E61B81A549CC" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_OtherServiceChargesMember" xlink:label="loc_wlkp_OtherServiceChargesMember_D04A578B8C70B2881122E61B81A58086" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_D28A9216B7F8BD21E421E61B81A5B0E8" xlink:to="loc_wlkp_OtherServiceChargesMember_D04A578B8C70B2881122E61B81A58086" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A80247F51514FDA07EABE61B81A51868" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_30A89DEBC819470918A6E61B81A55FE1" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A80247F51514FDA07EABE61B81A51868" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_F789E4D02D8A958673FFE61B81A5AC77_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A80247F51514FDA07EABE61B81A51868" xlink:to="loc_us-gaap_RelatedPartyDomain_F789E4D02D8A958673FFE61B81A5AC77_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_F789E4D02D8A958673FFE61B81A5AC77" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A80247F51514FDA07EABE61B81A51868" xlink:to="loc_us-gaap_RelatedPartyDomain_F789E4D02D8A958673FFE61B81A5AC77" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:label="loc_us-gaap_AffiliatedEntityMember_62AA23D3A96E2956D8D2E61B81A5915E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_F789E4D02D8A958673FFE61B81A5AC77" xlink:to="loc_us-gaap_AffiliatedEntityMember_62AA23D3A96E2956D8D2E61B81A5915E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_E78D9CE011723A3FC7A7E61B81A53661" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_30A89DEBC819470918A6E61B81A55FE1" xlink:to="loc_us-gaap_CounterpartyNameAxis_E78D9CE011723A3FC7A7E61B81A53661" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B1800B5A49A8460D6E8BE61B81A5FD18_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_E78D9CE011723A3FC7A7E61B81A53661" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B1800B5A49A8460D6E8BE61B81A5FD18_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B1800B5A49A8460D6E8BE61B81A5FD18" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_E78D9CE011723A3FC7A7E61B81A53661" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B1800B5A49A8460D6E8BE61B81A5FD18" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_2FD54C85D19A3651137EE61B81A568E2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B1800B5A49A8460D6E8BE61B81A5FD18" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_2FD54C85D19A3651137EE61B81A568E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartiesAmountInCostOfSales" xlink:label="loc_us-gaap_RelatedPartiesAmountInCostOfSales_3CF1E568A8D846EAC800E61B81A54D90" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_887781459BCA38C5411FE61B81A5025B" xlink:to="loc_us-gaap_RelatedPartiesAmountInCostOfSales_3CF1E568A8D846EAC800E61B81A54D90" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactionsDebtPayableToRelatedPartiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_64D35D23ECE8529BCB8A83E3C2B0A915" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5F69939557506D73B6BF83E3C2AE56EE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_64D35D23ECE8529BCB8A83E3C2B0A915" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5F69939557506D73B6BF83E3C2AE56EE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_C6DBFB25A397A2ABBD2283E3C2AF884C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5F69939557506D73B6BF83E3C2AE56EE" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_C6DBFB25A397A2ABBD2283E3C2AF884C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_00FB2884CD92DC495D6B83E3C2AF0BBF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_C6DBFB25A397A2ABBD2283E3C2AF884C" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_00FB2884CD92DC495D6B83E3C2AF0BBF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_00FB2884CD92DC495D6B83E3C2AF0BBF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_C6DBFB25A397A2ABBD2283E3C2AF884C" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_00FB2884CD92DC495D6B83E3C2AF0BBF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_D19DC2D097A0733C44AA83E3C2AF819F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_00FB2884CD92DC495D6B83E3C2AF0BBF" xlink:to="loc_us-gaap_SeniorNotesMember_D19DC2D097A0733C44AA83E3C2AF819F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_0BA2357B76B5ED1056AC83E3C2AF51A1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5F69939557506D73B6BF83E3C2AE56EE" xlink:to="loc_dei_LegalEntityAxis_0BA2357B76B5ED1056AC83E3C2AF51A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_823565DF1F59A1A6642783E3C2AFE0ED_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_0BA2357B76B5ED1056AC83E3C2AF51A1" xlink:to="loc_dei_EntityDomain_823565DF1F59A1A6642783E3C2AFE0ED_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_823565DF1F59A1A6642783E3C2AFE0ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_0BA2357B76B5ED1056AC83E3C2AF51A1" xlink:to="loc_dei_EntityDomain_823565DF1F59A1A6642783E3C2AFE0ED" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_B815CFE22361CBD6568483E3C2AF4231" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_823565DF1F59A1A6642783E3C2AFE0ED" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_B815CFE22361CBD6568483E3C2AF4231" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis" xlink:label="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_363EC3EF553C32B9CC8B83E3C2AF2800" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5F69939557506D73B6BF83E3C2AE56EE" xlink:to="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_363EC3EF553C32B9CC8B83E3C2AF2800" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_5C826984EBAF9840DC3183E3C2AF33AB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_363EC3EF553C32B9CC8B83E3C2AF2800" xlink:to="loc_us-gaap_DistributionTypeDomain_5C826984EBAF9840DC3183E3C2AF33AB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_5C826984EBAF9840DC3183E3C2AF33AB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_363EC3EF553C32B9CC8B83E3C2AF2800" xlink:to="loc_us-gaap_DistributionTypeDomain_5C826984EBAF9840DC3183E3C2AF33AB" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CashDistributionTrancheOneMember" xlink:label="loc_wlkp_CashDistributionTrancheOneMember_183DE857B3F920D1253D83E3C2AFCEC6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionTypeDomain_5C826984EBAF9840DC3183E3C2AF33AB" xlink:to="loc_wlkp_CashDistributionTrancheOneMember_183DE857B3F920D1253D83E3C2AFCEC6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_3DE3621C597064C60C7983E3C2AFD620" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5F69939557506D73B6BF83E3C2AE56EE" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_3DE3621C597064C60C7983E3C2AFD620" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_7BB0D2B61BFBC352C1FF83E3C2AFCFF2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_3DE3621C597064C60C7983E3C2AFD620" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_7BB0D2B61BFBC352C1FF83E3C2AFCFF2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_7BB0D2B61BFBC352C1FF83E3C2AFCFF2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_3DE3621C597064C60C7983E3C2AFD620" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_7BB0D2B61BFBC352C1FF83E3C2AFCFF2" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_165B2AC19EB1780B9E5D83E3C2B0DF55" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_7BB0D2B61BFBC352C1FF83E3C2AFCFF2" xlink:to="loc_wlkp_IDRHoldersMember_165B2AC19EB1780B9E5D83E3C2B0DF55" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_B144EFAD5CB02A4489E283E3C2B06492" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5F69939557506D73B6BF83E3C2AE56EE" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_B144EFAD5CB02A4489E283E3C2B06492" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_AB47CF451B2B2D9AAD4883E3C2B00674_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_B144EFAD5CB02A4489E283E3C2B06492" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_AB47CF451B2B2D9AAD4883E3C2B00674_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_AB47CF451B2B2D9AAD4883E3C2B00674" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_B144EFAD5CB02A4489E283E3C2B06492" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_AB47CF451B2B2D9AAD4883E3C2B00674" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccruedLiabilitiesMember" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_B3E096EA5DAF619A979683E3C2B0BE24" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_AB47CF451B2B2D9AAD4883E3C2B00674" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_B3E096EA5DAF619A979683E3C2B0BE24" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_5AF391552C668804CD2583E3C2B020F3" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5F69939557506D73B6BF83E3C2AE56EE" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_5AF391552C668804CD2583E3C2B020F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_70547445047755BB857683E3C2B0696B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_5AF391552C668804CD2583E3C2B020F3" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_70547445047755BB857683E3C2B0696B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_70547445047755BB857683E3C2B0696B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_5AF391552C668804CD2583E3C2B020F3" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_70547445047755BB857683E3C2B0696B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpenseMember" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpenseMember_29C3378E371504B96F5683E3C2B0B79E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_70547445047755BB857683E3C2B0696B" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpenseMember_29C3378E371504B96F5683E3C2B0B79E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F03061532F47F5D2BD1683E3C2B01A29" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5F69939557506D73B6BF83E3C2AE56EE" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F03061532F47F5D2BD1683E3C2B01A29" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_645688D94EEE733FDA7083E3C2B06291_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F03061532F47F5D2BD1683E3C2B01A29" xlink:to="loc_us-gaap_RelatedPartyDomain_645688D94EEE733FDA7083E3C2B06291_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_645688D94EEE733FDA7083E3C2B06291" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_F03061532F47F5D2BD1683E3C2B01A29" xlink:to="loc_us-gaap_RelatedPartyDomain_645688D94EEE733FDA7083E3C2B06291" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:label="loc_us-gaap_AffiliatedEntityMember_43C4869078DDCFD0030B83E3C2B0CBFA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_645688D94EEE733FDA7083E3C2B06291" xlink:to="loc_us-gaap_AffiliatedEntityMember_43C4869078DDCFD0030B83E3C2B0CBFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_F7878AE24EBB05E706F083E3C2B0EBD6" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_5F69939557506D73B6BF83E3C2AE56EE" xlink:to="loc_us-gaap_CounterpartyNameAxis_F7878AE24EBB05E706F083E3C2B0EBD6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B3178F1FA3518149AC7D83E3C2B05906_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_F7878AE24EBB05E706F083E3C2B0EBD6" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B3178F1FA3518149AC7D83E3C2B05906_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B3178F1FA3518149AC7D83E3C2B05906" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_F7878AE24EBB05E706F083E3C2B0EBD6" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B3178F1FA3518149AC7D83E3C2B05906" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_F8D64ECE7BC92F0B07E883E3C2B0E6A6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B3178F1FA3518149AC7D83E3C2B05906" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_F8D64ECE7BC92F0B07E883E3C2B0E6A6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpenseRelatedParty" xlink:label="loc_us-gaap_InterestExpenseRelatedParty_17CE08732C8C4555FD6C83E3C2B003FE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_64D35D23ECE8529BCB8A83E3C2B0A915" xlink:to="loc_us-gaap_InterestExpenseRelatedParty_17CE08732C8C4555FD6C83E3C2B003FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestCostsCapitalized" xlink:label="loc_us-gaap_InterestCostsCapitalized_F9EC0F563F81AE54BB7483E3C2B016EE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_64D35D23ECE8529BCB8A83E3C2B0A915" xlink:to="loc_us-gaap_InterestCostsCapitalized_F9EC0F563F81AE54BB7483E3C2B016EE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestPayableCurrent" xlink:label="loc_us-gaap_InterestPayableCurrent_C74066173C546984EB5C83E3C2B11131" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_64D35D23ECE8529BCB8A83E3C2B0A915" xlink:to="loc_us-gaap_InterestPayableCurrent_C74066173C546984EB5C83E3C2B11131" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DueToRelatedPartiesNoncurrent" xlink:label="loc_us-gaap_DueToRelatedPartiesNoncurrent_EE72AA6BFA2795B8DB9083E3C2B1759D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_64D35D23ECE8529BCB8A83E3C2B0A915" xlink:to="loc_us-gaap_DueToRelatedPartiesNoncurrent_EE72AA6BFA2795B8DB9083E3C2B1759D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactionsGeneralDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_A9B7FE2BECAFD5E1F137E61B82512757" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C5EFBFC6F8C2A821D33DE61B82512A43" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_A9B7FE2BECAFD5E1F137E61B82512757" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C5EFBFC6F8C2A821D33DE61B82512A43" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis" xlink:label="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_713294721BAB540BC838E61B82514C15" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C5EFBFC6F8C2A821D33DE61B82512A43" xlink:to="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_713294721BAB540BC838E61B82514C15" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_987A59283419F2A7C31FE61B82515186_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_713294721BAB540BC838E61B82514C15" xlink:to="loc_us-gaap_DistributionTypeDomain_987A59283419F2A7C31FE61B82515186_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_987A59283419F2A7C31FE61B82515186" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_713294721BAB540BC838E61B82514C15" xlink:to="loc_us-gaap_DistributionTypeDomain_987A59283419F2A7C31FE61B82515186" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CashDistributionTrancheOneMember" xlink:label="loc_wlkp_CashDistributionTrancheOneMember_5A408079E4531D91CFC0E61B8251EB1A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionTypeDomain_987A59283419F2A7C31FE61B82515186" xlink:to="loc_wlkp_CashDistributionTrancheOneMember_5A408079E4531D91CFC0E61B8251EB1A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_D3268C5D64E311E8BDFBE61B825131FA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C5EFBFC6F8C2A821D33DE61B82512A43" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_D3268C5D64E311E8BDFBE61B825131FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_90F142C04C25E8F3B81DE61B8251003E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_D3268C5D64E311E8BDFBE61B825131FA" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_90F142C04C25E8F3B81DE61B8251003E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_90F142C04C25E8F3B81DE61B8251003E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_D3268C5D64E311E8BDFBE61B825131FA" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_90F142C04C25E8F3B81DE61B8251003E" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_CBE27B6B306A5414778CE61B8251FDCF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_90F142C04C25E8F3B81DE61B8251003E" xlink:to="loc_wlkp_IDRHoldersMember_CBE27B6B306A5414778CE61B8251FDCF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_4CF325AA72D840098386E61B8251E3BF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C5EFBFC6F8C2A821D33DE61B82512A43" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_4CF325AA72D840098386E61B8251E3BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_CA0A3800ABBACB975ADCE61B82517CEF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_4CF325AA72D840098386E61B8251E3BF" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_CA0A3800ABBACB975ADCE61B82517CEF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_CA0A3800ABBACB975ADCE61B82517CEF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_4CF325AA72D840098386E61B8251E3BF" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_CA0A3800ABBACB975ADCE61B82517CEF" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SiteLeaseAgreementMember" xlink:label="loc_wlkp_SiteLeaseAgreementMember_597A6DAEA59BD17A18CCE61B8251FCD1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_CA0A3800ABBACB975ADCE61B82517CEF" xlink:to="loc_wlkp_SiteLeaseAgreementMember_597A6DAEA59BD17A18CCE61B8251FCD1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3B5F50541761F17456DAE61B8251032C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C5EFBFC6F8C2A821D33DE61B82512A43" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3B5F50541761F17456DAE61B8251032C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_3A75C03AAE5B216CE097E61B8251E653_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3B5F50541761F17456DAE61B8251032C" xlink:to="loc_us-gaap_RelatedPartyDomain_3A75C03AAE5B216CE097E61B8251E653_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_3A75C03AAE5B216CE097E61B8251E653" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3B5F50541761F17456DAE61B8251032C" xlink:to="loc_us-gaap_RelatedPartyDomain_3A75C03AAE5B216CE097E61B8251E653" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:label="loc_us-gaap_AffiliatedEntityMember_E43732D5654F752E45C3E61B8251819D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_3A75C03AAE5B216CE097E61B8251E653" xlink:to="loc_us-gaap_AffiliatedEntityMember_E43732D5654F752E45C3E61B8251819D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_4057C57D0FE6ABC1FAA6E61B82518E3B" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C5EFBFC6F8C2A821D33DE61B82512A43" xlink:to="loc_us-gaap_CounterpartyNameAxis_4057C57D0FE6ABC1FAA6E61B82518E3B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_50CBA289469701BC8382E61B82516ACB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_4057C57D0FE6ABC1FAA6E61B82518E3B" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_50CBA289469701BC8382E61B82516ACB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_50CBA289469701BC8382E61B82516ACB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_4057C57D0FE6ABC1FAA6E61B82518E3B" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_50CBA289469701BC8382E61B82516ACB" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_C22088B26E0CE6F0FC20E61B8251CA60" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_50CBA289469701BC8382E61B82516ACB" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_C22088B26E0CE6F0FC20E61B8251CA60" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_61A071D18D0E5CDB24A0E61B8251553A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C5EFBFC6F8C2A821D33DE61B82512A43" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_61A071D18D0E5CDB24A0E61B8251553A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2627F767B5AA55DEC68FE61B825111F4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_61A071D18D0E5CDB24A0E61B8251553A" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2627F767B5AA55DEC68FE61B825111F4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2627F767B5AA55DEC68FE61B825111F4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_61A071D18D0E5CDB24A0E61B8251553A" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2627F767B5AA55DEC68FE61B825111F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_2CF45DC98BE92DAE0EC7E61B825170FC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2627F767B5AA55DEC68FE61B825111F4" xlink:to="loc_us-gaap_SeniorNotesMember_2CF45DC98BE92DAE0EC7E61B825170FC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_CFB8FB665BE146FB4F77E61B8251646C" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C5EFBFC6F8C2A821D33DE61B82512A43" xlink:to="loc_dei_LegalEntityAxis_CFB8FB665BE146FB4F77E61B8251646C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_20FA03F38D02F6882622E61B82516909_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_CFB8FB665BE146FB4F77E61B8251646C" xlink:to="loc_dei_EntityDomain_20FA03F38D02F6882622E61B82516909_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_20FA03F38D02F6882622E61B82516909" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_CFB8FB665BE146FB4F77E61B8251646C" xlink:to="loc_dei_EntityDomain_20FA03F38D02F6882622E61B82516909" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_WestlakeChemicalOpCoLPMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoLPMember_D4034C79CD8A7E28C638E61B82514832" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_20FA03F38D02F6882622E61B82516909" xlink:to="loc_wlkp_WestlakeChemicalOpCoLPMember_D4034C79CD8A7E28C638E61B82514832" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_B4C71C57EC3C4AD11F7FE61B825123DC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_20FA03F38D02F6882622E61B82516909" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_B4C71C57EC3C4AD11F7FE61B825123DC" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_Shortfallpercentagethreshold" xlink:label="loc_wlkp_Shortfallpercentagethreshold_6001DF646B11E25DB933E61B8251D9A6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_A9B7FE2BECAFD5E1F137E61B82512757" xlink:to="loc_wlkp_Shortfallpercentagethreshold_6001DF646B11E25DB933E61B8251D9A6" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_Buyerdeficiencyfee" xlink:label="loc_wlkp_Buyerdeficiencyfee_11B218220596EE610868E61B82511E18" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_A9B7FE2BECAFD5E1F137E61B82512757" xlink:to="loc_wlkp_Buyerdeficiencyfee_11B218220596EE610868E61B82511E18" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactionsGoodsAndServicesFromRelatedPartiesThatHaveBeenCapitalizedDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_DF77B4F5CA4DD9027B8AE61B819689D5" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_DC8B231DE9830973C432E61B81967E72" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_DF77B4F5CA4DD9027B8AE61B819689D5" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_DC8B231DE9830973C432E61B81967E72" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_05D02BE1066D89C0E478E61B8196FBF9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_DC8B231DE9830973C432E61B81967E72" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_05D02BE1066D89C0E478E61B8196FBF9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_D86A0CB070FF2C5278C5E61B8196D2A8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_05D02BE1066D89C0E478E61B8196FBF9" xlink:to="loc_us-gaap_RelatedPartyDomain_D86A0CB070FF2C5278C5E61B8196D2A8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_D86A0CB070FF2C5278C5E61B8196D2A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_05D02BE1066D89C0E478E61B8196FBF9" xlink:to="loc_us-gaap_RelatedPartyDomain_D86A0CB070FF2C5278C5E61B8196D2A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:label="loc_us-gaap_AffiliatedEntityMember_EFBDE56C61933DC5B426E61B8196624E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_D86A0CB070FF2C5278C5E61B8196D2A8" xlink:to="loc_us-gaap_AffiliatedEntityMember_EFBDE56C61933DC5B426E61B8196624E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_EECE6D2666DF996803C8E61B8196BE5E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_DC8B231DE9830973C432E61B81967E72" xlink:to="loc_us-gaap_CounterpartyNameAxis_EECE6D2666DF996803C8E61B8196BE5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6524113AAEB85F71146DE61B81960B34_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_EECE6D2666DF996803C8E61B8196BE5E" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6524113AAEB85F71146DE61B81960B34_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6524113AAEB85F71146DE61B81960B34" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_EECE6D2666DF996803C8E61B8196BE5E" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6524113AAEB85F71146DE61B81960B34" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_A235628E8DB9AB46FB3EE61B8196936D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_6524113AAEB85F71146DE61B81960B34" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_A235628E8DB9AB46FB3EE61B8196936D" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_RelatedPartyTransactionPurchasesFromRelatedPartyCapitalizedAsAssets" xlink:label="loc_wlkp_RelatedPartyTransactionPurchasesFromRelatedPartyCapitalizedAsAssets_D1C96204BE13C91786C7E61B81967981" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_DF77B4F5CA4DD9027B8AE61B819689D5" xlink:to="loc_wlkp_RelatedPartyTransactionPurchasesFromRelatedPartyCapitalizedAsAssets_D1C96204BE13C91786C7E61B81967981" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactionsSalesToRelatedPartiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_F0B947BC6964352BE729E61B8242F5A1" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_B148F911759B152F4D49E61B8242938F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0B947BC6964352BE729E61B8242F5A1" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_B148F911759B152F4D49E61B8242938F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_ADBA9FD2709BDF947701E61B82425035" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_B148F911759B152F4D49E61B8242938F" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_ADBA9FD2709BDF947701E61B82425035" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_C3EA538BC8E1942BD349E61B82421C09_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_ADBA9FD2709BDF947701E61B82425035" xlink:to="loc_us-gaap_RelatedPartyDomain_C3EA538BC8E1942BD349E61B82421C09_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_C3EA538BC8E1942BD349E61B82421C09" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_ADBA9FD2709BDF947701E61B82425035" xlink:to="loc_us-gaap_RelatedPartyDomain_C3EA538BC8E1942BD349E61B82421C09" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:label="loc_us-gaap_AffiliatedEntityMember_72637F3D7B86F6BEEEC4E61B82429985" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_C3EA538BC8E1942BD349E61B82421C09" xlink:to="loc_us-gaap_AffiliatedEntityMember_72637F3D7B86F6BEEEC4E61B82429985" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_5ED50D5B71CF37F3D9F5E61B824211D6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_B148F911759B152F4D49E61B8242938F" xlink:to="loc_us-gaap_CounterpartyNameAxis_5ED50D5B71CF37F3D9F5E61B824211D6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_35FB6E8A4D9DBE19D684E61B8242DB37_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_5ED50D5B71CF37F3D9F5E61B824211D6" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_35FB6E8A4D9DBE19D684E61B8242DB37_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_35FB6E8A4D9DBE19D684E61B8242DB37" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_5ED50D5B71CF37F3D9F5E61B824211D6" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_35FB6E8A4D9DBE19D684E61B8242DB37" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_0A2B447072DF17E6A875E61B824224C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_35FB6E8A4D9DBE19D684E61B8242DB37" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_0A2B447072DF17E6A875E61B824224C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueFromRelatedParties" xlink:label="loc_us-gaap_RevenueFromRelatedParties_8DAD749ADC958B4D3FA6E61B8242EE37" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_F0B947BC6964352BE729E61B8242F5A1" xlink:to="loc_us-gaap_RevenueFromRelatedParties_8DAD749ADC958B4D3FA6E61B8242EE37" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactionsServicesFromRelatedPartiesIncludedInSgaExpensesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_4B22D2B053E81333C495E61B806D912D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_677D1405864DEB57229BE61B806D0F28" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_4B22D2B053E81333C495E61B806D912D" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_677D1405864DEB57229BE61B806D0F28" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3BD32DE7D3B12D635761E61B806DB427" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_677D1405864DEB57229BE61B806D0F28" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3BD32DE7D3B12D635761E61B806DB427" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_041785B46689E2BF9C73E61B806D269D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3BD32DE7D3B12D635761E61B806DB427" xlink:to="loc_us-gaap_RelatedPartyDomain_041785B46689E2BF9C73E61B806D269D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_041785B46689E2BF9C73E61B806D269D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3BD32DE7D3B12D635761E61B806DB427" xlink:to="loc_us-gaap_RelatedPartyDomain_041785B46689E2BF9C73E61B806D269D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:label="loc_us-gaap_AffiliatedEntityMember_D05D576B30A2EC6F3C98E61B806DB1ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_041785B46689E2BF9C73E61B806D269D" xlink:to="loc_us-gaap_AffiliatedEntityMember_D05D576B30A2EC6F3C98E61B806DB1ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_C0AB22C277DA7B901483E61B806DE3EC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_677D1405864DEB57229BE61B806D0F28" xlink:to="loc_us-gaap_CounterpartyNameAxis_C0AB22C277DA7B901483E61B806DE3EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B8033AB36B46581ADAE9E61B806D259D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_C0AB22C277DA7B901483E61B806DE3EC" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B8033AB36B46581ADAE9E61B806D259D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B8033AB36B46581ADAE9E61B806D259D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_C0AB22C277DA7B901483E61B806DE3EC" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B8033AB36B46581ADAE9E61B806D259D" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_54702F0E0500EF0A3338E61B806D9FDA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_B8033AB36B46581ADAE9E61B806D259D" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_54702F0E0500EF0A3338E61B806D9FDA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty" xlink:label="loc_us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty_9AF98C41D0F3BBA724E2E61B806D481E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_4B22D2B053E81333C495E61B806D912D" xlink:to="loc_us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty_9AF98C41D0F3BBA724E2E61B806D481E" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactionsSiteLeaseAgreementsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_CC39E1B743383EE758B4E61B8157E18E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_E45E25C4730B726407C1E61B8157E365" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_CC39E1B743383EE758B4E61B8157E18E" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_E45E25C4730B726407C1E61B8157E365" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_357B6F7CEFDD2EA45A99E61B8157FC55" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_E45E25C4730B726407C1E61B8157E365" xlink:to="loc_dei_LegalEntityAxis_357B6F7CEFDD2EA45A99E61B8157FC55" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_B3C06C3EFDF78667BAEAE61B8157DDBD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_357B6F7CEFDD2EA45A99E61B8157FC55" xlink:to="loc_dei_EntityDomain_B3C06C3EFDF78667BAEAE61B8157DDBD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_B3C06C3EFDF78667BAEAE61B8157DDBD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_357B6F7CEFDD2EA45A99E61B8157FC55" xlink:to="loc_dei_EntityDomain_B3C06C3EFDF78667BAEAE61B8157DDBD" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_WestlakeChemicalOpCoLPMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoLPMember_9CD6845F1E30D0C44B0AE61B8157C5C2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_B3C06C3EFDF78667BAEAE61B8157DDBD" xlink:to="loc_wlkp_WestlakeChemicalOpCoLPMember_9CD6845F1E30D0C44B0AE61B8157C5C2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4DFD68B5B510FDE38943E61B81573998" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_E45E25C4730B726407C1E61B8157E365" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4DFD68B5B510FDE38943E61B81573998" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_861BD84926FB5CCA1925E61B8157F68F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4DFD68B5B510FDE38943E61B81573998" xlink:to="loc_us-gaap_RelatedPartyDomain_861BD84926FB5CCA1925E61B8157F68F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_861BD84926FB5CCA1925E61B8157F68F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4DFD68B5B510FDE38943E61B81573998" xlink:to="loc_us-gaap_RelatedPartyDomain_861BD84926FB5CCA1925E61B8157F68F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:label="loc_us-gaap_AffiliatedEntityMember_0EF0BC3A94F8A9AFBD72E61B8157E91B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_861BD84926FB5CCA1925E61B8157F68F" xlink:to="loc_us-gaap_AffiliatedEntityMember_0EF0BC3A94F8A9AFBD72E61B8157E91B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_85E5565B32547C8BA40AE61B81578FB8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_E45E25C4730B726407C1E61B8157E365" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_85E5565B32547C8BA40AE61B81578FB8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_F4CADB0177C0B920F652E61B8157477C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_85E5565B32547C8BA40AE61B81578FB8" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_F4CADB0177C0B920F652E61B8157477C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_F4CADB0177C0B920F652E61B8157477C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_85E5565B32547C8BA40AE61B81578FB8" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_F4CADB0177C0B920F652E61B8157477C" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_SiteLeaseAgreementMember" xlink:label="loc_wlkp_SiteLeaseAgreementMember_CE10161C91B652978B59E61B8157A745" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_F4CADB0177C0B920F652E61B8157477C" xlink:to="loc_wlkp_SiteLeaseAgreementMember_CE10161C91B652978B59E61B8157A745" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_LesseeLeasingArrangementsOperatingLeasesNumber" xlink:label="loc_wlkp_LesseeLeasingArrangementsOperatingLeasesNumber_116A558382B2962A17A1E61B81577BAA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_CC39E1B743383EE758B4E61B8157E18E" xlink:to="loc_wlkp_LesseeLeasingArrangementsOperatingLeasesNumber_116A558382B2962A17A1E61B81577BAA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract" xlink:label="loc_us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract_B2A074F2DB4279679E67E61B815767F8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_CC39E1B743383EE758B4E61B8157E18E" xlink:to="loc_us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract_B2A074F2DB4279679E67E61B815767F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LeaseAndRentalExpense" xlink:label="loc_us-gaap_LeaseAndRentalExpense_97F3F2DA703B7CFD2409E61B8157597C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_CC39E1B743383EE758B4E61B8157E18E" xlink:to="loc_us-gaap_LeaseAndRentalExpense_97F3F2DA703B7CFD2409E61B8157597C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactionsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/SubsequentEvents" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:label="loc_us-gaap_SubsequentEventLineItems_371C2800E388A87DA24C5C8FE87887A9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="loc_us-gaap_SubsequentEventTable_6E1BAF7B7B7F9F32BCC65C8FE8735488" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_371C2800E388A87DA24C5C8FE87887A9" xlink:to="loc_us-gaap_SubsequentEventTable_6E1BAF7B7B7F9F32BCC65C8FE8735488" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis" xlink:label="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_4F266D62DBE5996570CB5C8FE873A80F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_6E1BAF7B7B7F9F32BCC65C8FE8735488" xlink:to="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_4F266D62DBE5996570CB5C8FE873A80F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_AC1CCD8C34DCA8A3E0D65C8FE874C42E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_4F266D62DBE5996570CB5C8FE873A80F" xlink:to="loc_us-gaap_DistributionTypeDomain_AC1CCD8C34DCA8A3E0D65C8FE874C42E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_AC1CCD8C34DCA8A3E0D65C8FE874C42E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_4F266D62DBE5996570CB5C8FE873A80F" xlink:to="loc_us-gaap_DistributionTypeDomain_AC1CCD8C34DCA8A3E0D65C8FE874C42E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashDistributionMember" xlink:label="loc_us-gaap_CashDistributionMember_445B3C530061ABFBF4345C8FE874050D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionTypeDomain_AC1CCD8C34DCA8A3E0D65C8FE874C42E" xlink:to="loc_us-gaap_CashDistributionMember_445B3C530061ABFBF4345C8FE874050D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2812DC8B1026E1E08B465C8FE8747092" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_6E1BAF7B7B7F9F32BCC65C8FE8735488" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2812DC8B1026E1E08B465C8FE8747092" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9154831618C71DA783EB5C8FE8748F1B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2812DC8B1026E1E08B465C8FE8747092" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9154831618C71DA783EB5C8FE8748F1B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9154831618C71DA783EB5C8FE8748F1B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2812DC8B1026E1E08B465C8FE8747092" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9154831618C71DA783EB5C8FE8748F1B" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_CommonAndSubordinatedUnitsMember" xlink:label="loc_wlkp_CommonAndSubordinatedUnitsMember_429AF73A8BCD187F2D265C8FE8744AF2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_9154831618C71DA783EB5C8FE8748F1B" xlink:to="loc_wlkp_CommonAndSubordinatedUnitsMember_429AF73A8BCD187F2D265C8FE8744AF2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_6941A9F281D7BD1249D15C8FE87454AB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_6E1BAF7B7B7F9F32BCC65C8FE8735488" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_6941A9F281D7BD1249D15C8FE87454AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_1F68E6477118413B2A225C8FE878EF2C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_6941A9F281D7BD1249D15C8FE87454AB" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_1F68E6477118413B2A225C8FE878EF2C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_1F68E6477118413B2A225C8FE878EF2C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_6941A9F281D7BD1249D15C8FE87454AB" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_1F68E6477118413B2A225C8FE878EF2C" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20170930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_FF654772FC583865B8A65C8FE878D744" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_1F68E6477118413B2A225C8FE878EF2C" xlink:to="loc_wlkp_IDRHoldersMember_FF654772FC583865B8A65C8FE878D744" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_D31A5695328B2D7F76B25C8FE87803C4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_6E1BAF7B7B7F9F32BCC65C8FE8735488" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_D31A5695328B2D7F76B25C8FE87803C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_64C2CD018665E7196E315C8FE878CD1E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_D31A5695328B2D7F76B25C8FE87803C4" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_64C2CD018665E7196E315C8FE878CD1E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_64C2CD018665E7196E315C8FE878CD1E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_D31A5695328B2D7F76B25C8FE87803C4" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_64C2CD018665E7196E315C8FE878CD1E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_9F1265BD0F8C5A93CEF95C8FE8787B18" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_64C2CD018665E7196E315C8FE878CD1E" xlink:to="loc_us-gaap_SubsequentEventMember_9F1265BD0F8C5A93CEF95C8FE8787B18" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit" xlink:label="loc_us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit_10496CFB618A82FB9FD25C8FE878A393" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_371C2800E388A87DA24C5C8FE87887A9" xlink:to="loc_us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit_10496CFB618A82FB9FD25C8FE878A393" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncentiveDistributionDistributionPerYear" xlink:label="loc_us-gaap_IncentiveDistributionDistributionPerYear_6DA50D3EBC6FAD9DB6B15C8FE878669B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_371C2800E388A87DA24C5C8FE87887A9" xlink:to="loc_us-gaap_IncentiveDistributionDistributionPerYear_6DA50D3EBC6FAD9DB6B15C8FE878669B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/SupplementalInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/SupplementalInformationDetails" xlink:type="extended" />
</link:linkbase>
