<?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-20180930.xsd#AccountsReceivableThirdParties" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/AccountsReceivableThirdPartiesAccountsReceivablethirdPartiesScheduleOfAccountsReceivableDetails" xlink:href="wlkp-20180930.xsd#AccountsReceivableThirdPartiesAccountsReceivablethirdPartiesScheduleOfAccountsReceivableDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/AccountsReceivableThirdPartiesTables" xlink:href="wlkp-20180930.xsd#AccountsReceivableThirdPartiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/CommitmentsAndContingencies" xlink:href="wlkp-20180930.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedBalanceSheets" xlink:href="wlkp-20180930.xsd#ConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:href="wlkp-20180930.xsd#ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedStatementsOfCashFlows" xlink:href="wlkp-20180930.xsd#ConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedStatementsOfChangesInEquity" xlink:href="wlkp-20180930.xsd#ConsolidatedStatementsOfChangesInEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedStatementsOfOperations" xlink:href="wlkp-20180930.xsd#ConsolidatedStatementsOfOperations" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DescriptionOfBusinessAndBasisOfPresentation" xlink:href="wlkp-20180930.xsd#DescriptionOfBusinessAndBasisOfPresentation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DescriptionOfBusinessAndBasisOfPresentationDetails" xlink:href="wlkp-20180930.xsd#DescriptionOfBusinessAndBasisOfPresentationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DescriptionOfBusinessAndBasisOfPresentationPolicies" xlink:href="wlkp-20180930.xsd#DescriptionOfBusinessAndBasisOfPresentationPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnit" xlink:href="wlkp-20180930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnit" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitBasicAndDilutedIncomePerLimitedPartnerUnitDetails" xlink:href="wlkp-20180930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnitBasicAndDilutedIncomePerLimitedPartnerUnitDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitDistributionPerCommonUnitDetails" xlink:href="wlkp-20180930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnitDistributionPerCommonUnitDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitDistributionsDeclaredDetails" xlink:href="wlkp-20180930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnitDistributionsDeclaredDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitIncomeInExcessOfDistributionDetails" xlink:href="wlkp-20180930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnitIncomeInExcessOfDistributionDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitTables" xlink:href="wlkp-20180930.xsd#DistributionsAndNetIncomePerLimitedPartnerUnitTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/DocumentAndEntityInformation" xlink:href="wlkp-20180930.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/FairValueMeasurements" xlink:href="wlkp-20180930.xsd#FairValueMeasurements" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/FairValueMeasurementsSummaryOfCarryingAndFairValuesOfLongTermDebtDetails" xlink:href="wlkp-20180930.xsd#FairValueMeasurementsSummaryOfCarryingAndFairValuesOfLongTermDebtDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/FairValueMeasurementsTables" xlink:href="wlkp-20180930.xsd#FairValueMeasurementsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/Inventories" xlink:href="wlkp-20180930.xsd#Inventories" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/InventoriesDetails" xlink:href="wlkp-20180930.xsd#InventoriesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/InventoriesTables" xlink:href="wlkp-20180930.xsd#InventoriesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/LongTermDebtPayableToWestlake" xlink:href="wlkp-20180930.xsd#LongTermDebtPayableToWestlake" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/LongTermDebtPayableToWestlakeDetails" xlink:href="wlkp-20180930.xsd#LongTermDebtPayableToWestlakeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/LongTermDebtPayableToWestlakeTables" xlink:href="wlkp-20180930.xsd#LongTermDebtPayableToWestlakeTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/OtherAssets" xlink:href="wlkp-20180930.xsd#OtherAssets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/OtherAssetsDetails" xlink:href="wlkp-20180930.xsd#OtherAssetsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/PartnersEquity" xlink:href="wlkp-20180930.xsd#PartnersEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/PartnersEquityDetails" xlink:href="wlkp-20180930.xsd#PartnersEquityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/PropertyPlantAndEquipment" xlink:href="wlkp-20180930.xsd#PropertyPlantAndEquipment" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/PropertyPlantAndEquipmentDetail" xlink:href="wlkp-20180930.xsd#PropertyPlantAndEquipmentDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactions" xlink:href="wlkp-20180930.xsd#RelatedPartyTransactions" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsAccountsReceivableFromAndAccountsPayableToRelatedPartiesDetails" xlink:href="wlkp-20180930.xsd#RelatedPartyTransactionsAccountsReceivableFromAndAccountsPayableToRelatedPartiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsCostOfSalesFromRelatedPartiesDetails" xlink:href="wlkp-20180930.xsd#RelatedPartyTransactionsCostOfSalesFromRelatedPartiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsDebtPayableToRelatedPartiesDetails" xlink:href="wlkp-20180930.xsd#RelatedPartyTransactionsDebtPayableToRelatedPartiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsGeneralDetails" xlink:href="wlkp-20180930.xsd#RelatedPartyTransactionsGeneralDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsGoodsAndServicesFromRelatedPartiesThatHaveBeenCapitalizedDetails" xlink:href="wlkp-20180930.xsd#RelatedPartyTransactionsGoodsAndServicesFromRelatedPartiesThatHaveBeenCapitalizedDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsMajorCustomerAndConcentrationRiskDetails" xlink:href="wlkp-20180930.xsd#RelatedPartyTransactionsMajorCustomerAndConcentrationRiskDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsServicesFromRelatedPartiesIncludedInSgaExpensesDetails" xlink:href="wlkp-20180930.xsd#RelatedPartyTransactionsServicesFromRelatedPartiesIncludedInSgaExpensesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsSiteLeaseAgreementsDetails" xlink:href="wlkp-20180930.xsd#RelatedPartyTransactionsSiteLeaseAgreementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/RelatedPartyTransactionsTables" xlink:href="wlkp-20180930.xsd#RelatedPartyTransactionsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/SubsequentEventsDetails" xlink:href="wlkp-20180930.xsd#SubsequentEventsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/SubsequentEventsSubsequentEvents" xlink:href="wlkp-20180930.xsd#SubsequentEventsSubsequentEvents" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/SubsequentEventsTables" xlink:href="wlkp-20180930.xsd#SubsequentEventsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/SupplementalInformation" xlink:href="wlkp-20180930.xsd#SupplementalInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.westlake.com/role/SupplementalInformationDetails" xlink:href="wlkp-20180930.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/CommitmentsAndContingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_06A1A8FC94A88FC59C2F88A7D22D1B2B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_7547EB3CC3F0DF0BB54888A7D22D3785" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_06A1A8FC94A88FC59C2F88A7D22D1B2B" xlink:to="loc_us-gaap_StatementTable_7547EB3CC3F0DF0BB54888A7D22D3785" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_262298ED3EF126F5CD6F88A7D22D4B0A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_7547EB3CC3F0DF0BB54888A7D22D3785" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_262298ED3EF126F5CD6F88A7D22D4B0A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_DDF23CAE3E9C5EC22D2288A7D22D00DD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_262298ED3EF126F5CD6F88A7D22D4B0A" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_DDF23CAE3E9C5EC22D2288A7D22D00DD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_DDF23CAE3E9C5EC22D2288A7D22D00DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_262298ED3EF126F5CD6F88A7D22D4B0A" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_DDF23CAE3E9C5EC22D2288A7D22D00DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_D91CAFEA08EDD9C8663488A7D22D0503" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_DDF23CAE3E9C5EC22D2288A7D22D00DD" xlink:to="loc_us-gaap_LimitedPartnerMember_D91CAFEA08EDD9C8663488A7D22D0503" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GeneralPartnerMember" xlink:label="loc_us-gaap_GeneralPartnerMember_965ED94CF1290535414F88A7D22D1A4D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_DDF23CAE3E9C5EC22D2288A7D22D00DD" xlink:to="loc_us-gaap_GeneralPartnerMember_965ED94CF1290535414F88A7D22D1A4D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_44B98A5D7A2F763A341788A7D22DB332" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_7547EB3CC3F0DF0BB54888A7D22D3785" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_44B98A5D7A2F763A341788A7D22DB332" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_30D17AE80274A80C4E4688A7D22DF093_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_44B98A5D7A2F763A341788A7D22DB332" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_30D17AE80274A80C4E4688A7D22DF093_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_30D17AE80274A80C4E4688A7D22DF093" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_44B98A5D7A2F763A341788A7D22DB332" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_30D17AE80274A80C4E4688A7D22DF093" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_35C5AB8A61E0E323678D88A7D22DA6E2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_30D17AE80274A80C4E4688A7D22DF093" xlink:to="loc_wlkp_CommonUnitsMember_35C5AB8A61E0E323678D88A7D22DA6E2" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_541FA2791B1096B4AE5A88A7D22D80A3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_30D17AE80274A80C4E4688A7D22DF093" xlink:to="loc_wlkp_SubordinatedUnitsMember_541FA2791B1096B4AE5A88A7D22D80A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_16E1B8092698FB49C6B688A7D22DB258" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_7547EB3CC3F0DF0BB54888A7D22D3785" xlink:to="loc_srt_CounterpartyNameAxis_16E1B8092698FB49C6B688A7D22DB258" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_D3D562322BF0E6C6F9FA88A7D22DE151_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_16E1B8092698FB49C6B688A7D22DB258" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_D3D562322BF0E6C6F9FA88A7D22DE151_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_D3D562322BF0E6C6F9FA88A7D22DE151" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_16E1B8092698FB49C6B688A7D22DB258" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_D3D562322BF0E6C6F9FA88A7D22DE151" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_UnidentifiedThirdPartiesMember" xlink:label="loc_wlkp_UnidentifiedThirdPartiesMember_55FBA5458C0B8F6C17D688A7D22DC2D1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_D3D562322BF0E6C6F9FA88A7D22DE151" xlink:to="loc_wlkp_UnidentifiedThirdPartiesMember_55FBA5458C0B8F6C17D688A7D22DC2D1" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_8BBDBEFA33C997FC479688A7D22D857D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_D3D562322BF0E6C6F9FA88A7D22DE151" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_8BBDBEFA33C997FC479688A7D22D857D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="loc_us-gaap_AssetsAbstract_54E29642B1939855035E88A7D22D9E65" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_06A1A8FC94A88FC59C2F88A7D22D1B2B" xlink:to="loc_us-gaap_AssetsAbstract_54E29642B1939855035E88A7D22D9E65" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="loc_us-gaap_AssetsCurrentAbstract_D52B901FEB3655B0FFC788A7D22D21D1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_54E29642B1939855035E88A7D22D9E65" xlink:to="loc_us-gaap_AssetsCurrentAbstract_D52B901FEB3655B0FFC788A7D22D21D1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_A7BBBECD2B9694772F2E88A7D22D1504" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_D52B901FEB3655B0FFC788A7D22D21D1" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_A7BBBECD2B9694772F2E88A7D22D1504" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent" xlink:label="loc_wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent_9C602F9BCC8B1E02A2BF88A7D22D7D1F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_D52B901FEB3655B0FFC788A7D22D21D1" xlink:to="loc_wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent_9C602F9BCC8B1E02A2BF88A7D22D7D1F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsReceivableRelatedPartiesCurrent" xlink:label="loc_us-gaap_AccountsReceivableRelatedPartiesCurrent_B4D17F7844E660C1561388A7D22D7EE3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_D52B901FEB3655B0FFC788A7D22D21D1" xlink:to="loc_us-gaap_AccountsReceivableRelatedPartiesCurrent_B4D17F7844E660C1561388A7D22D7EE3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ReceivablesNetCurrent" xlink:label="loc_us-gaap_ReceivablesNetCurrent_328E00FA15AC0ADEEC9E88A7D22DA9E0" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_D52B901FEB3655B0FFC788A7D22D21D1" xlink:to="loc_us-gaap_ReceivablesNetCurrent_328E00FA15AC0ADEEC9E88A7D22DA9E0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InventoryNet" xlink:label="loc_us-gaap_InventoryNet_6DFB0F4DD553AA75E4EA88A7D22DBA2B" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_D52B901FEB3655B0FFC788A7D22D21D1" xlink:to="loc_us-gaap_InventoryNet_6DFB0F4DD553AA75E4EA88A7D22DBA2B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_FB74250933C3DABF52C888A7D22DE2F9" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_D52B901FEB3655B0FFC788A7D22D21D1" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_FB74250933C3DABF52C888A7D22DE2F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaap_AssetsCurrent_513E6FA18FB63B12B4C288A7D22DAB99" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_D52B901FEB3655B0FFC788A7D22D21D1" xlink:to="loc_us-gaap_AssetsCurrent_513E6FA18FB63B12B4C288A7D22DAB99" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_22282549406D60267AC988A7D22D1035" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_54E29642B1939855035E88A7D22D9E65" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_22282549406D60267AC988A7D22D1035" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherAssetsAbstract" xlink:label="loc_us-gaap_OtherAssetsAbstract_2AC63099E21A9D050A8888A7D22D3491" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_54E29642B1939855035E88A7D22D9E65" xlink:to="loc_us-gaap_OtherAssetsAbstract_2AC63099E21A9D050A8888A7D22D3491" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_0B3C94F8E063454A4EB288A7D22DBAA3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_2AC63099E21A9D050A8888A7D22D3491" xlink:to="loc_us-gaap_Goodwill_0B3C94F8E063454A4EB288A7D22DBAA3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredCostsAndOtherAssets" xlink:label="loc_us-gaap_DeferredCostsAndOtherAssets_3E944BC0B5FBA6295AC988A7D22D40B5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_2AC63099E21A9D050A8888A7D22D3491" xlink:to="loc_us-gaap_DeferredCostsAndOtherAssets_3E944BC0B5FBA6295AC988A7D22D40B5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaap_Assets_CAE62A1022DFE87D4C7A88A7D22DAD56" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_54E29642B1939855035E88A7D22D9E65" xlink:to="loc_us-gaap_Assets_CAE62A1022DFE87D4C7A88A7D22DAD56" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_331E171A35DE318DBDF688A7D22DB13D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_06A1A8FC94A88FC59C2F88A7D22D1B2B" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_331E171A35DE318DBDF688A7D22DB13D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_9523999DD217157EB72F88A7D22DC4E2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_331E171A35DE318DBDF688A7D22DB13D" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_9523999DD217157EB72F88A7D22DC4E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsPayableRelatedPartiesCurrent" xlink:label="loc_us-gaap_AccountsPayableRelatedPartiesCurrent_4A067B9E5E71BCEB304F88A7D22D0BDB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_9523999DD217157EB72F88A7D22DC4E2" xlink:to="loc_us-gaap_AccountsPayableRelatedPartiesCurrent_4A067B9E5E71BCEB304F88A7D22D0BDB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="loc_us-gaap_AccountsPayableCurrent_C292F66E9085DD1DD49088A7D22D78C9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_9523999DD217157EB72F88A7D22DC4E2" xlink:to="loc_us-gaap_AccountsPayableCurrent_C292F66E9085DD1DD49088A7D22D78C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_EFAF24BAE09598A1228688A7D22D0E6A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_9523999DD217157EB72F88A7D22DC4E2" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_EFAF24BAE09598A1228688A7D22D0E6A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaap_LiabilitiesCurrent_A6349ADF87F7383CF81388A7D22D1CD0" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_9523999DD217157EB72F88A7D22DC4E2" xlink:to="loc_us-gaap_LiabilitiesCurrent_A6349ADF87F7383CF81388A7D22D1CD0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DueToRelatedPartiesNoncurrent" xlink:label="loc_us-gaap_DueToRelatedPartiesNoncurrent_E04AEC23871479F536A688A7D22D5230" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_331E171A35DE318DBDF688A7D22DB13D" xlink:to="loc_us-gaap_DueToRelatedPartiesNoncurrent_E04AEC23871479F536A688A7D22D5230" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxLiabilitiesNoncurrent" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesNoncurrent_FCAD70FA4CF81A12B37D88A7D22DB092" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_331E171A35DE318DBDF688A7D22DB13D" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesNoncurrent_FCAD70FA4CF81A12B37D88A7D22DB092" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_66763AB6A623BAC2914988A7D22D1EAC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_331E171A35DE318DBDF688A7D22DB13D" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_66763AB6A623BAC2914988A7D22D1EAC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_Liabilities" xlink:label="loc_us-gaap_Liabilities_033EAD91E8C8B298C36D88A7D22DFEFE" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_331E171A35DE318DBDF688A7D22DB13D" xlink:to="loc_us-gaap_Liabilities_033EAD91E8C8B298C36D88A7D22DFEFE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="loc_us-gaap_CommitmentsAndContingencies_1E4E89CFD97FC0DEDCB688A7D22DBCC2" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_331E171A35DE318DBDF688A7D22DB13D" xlink:to="loc_us-gaap_CommitmentsAndContingencies_1E4E89CFD97FC0DEDCB688A7D22DBCC2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="loc_us-gaap_StockholdersEquityAbstract_69B7339380242F32FFB288A7D22D956D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_06A1A8FC94A88FC59C2F88A7D22D1B2B" xlink:to="loc_us-gaap_StockholdersEquityAbstract_69B7339380242F32FFB288A7D22D956D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccount" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccount_20765BA477E20064BCE588A7D22D41B5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_69B7339380242F32FFB288A7D22D956D" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccount_20765BA477E20064BCE588A7D22D41B5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GeneralPartnersCapitalAccount" xlink:label="loc_us-gaap_GeneralPartnersCapitalAccount_1D751DB5ADA8EC13AB5D88A7D22D97CB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_69B7339380242F32FFB288A7D22D956D" xlink:to="loc_us-gaap_GeneralPartnersCapitalAccount_1D751DB5ADA8EC13AB5D88A7D22D97CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_2A8B50B3AD4D58A3F08888A7D22DB4B9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_69B7339380242F32FFB288A7D22D956D" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_2A8B50B3AD4D58A3F08888A7D22DB4B9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnersCapital" xlink:label="loc_us-gaap_PartnersCapital_5299FC4201AF185B27D588A7D22D758D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_69B7339380242F32FFB288A7D22D956D" xlink:to="loc_us-gaap_PartnersCapital_5299FC4201AF185B27D588A7D22D758D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MinorityInterestInLimitedPartnerships" xlink:label="loc_us-gaap_MinorityInterestInLimitedPartnerships_61E08AD0E2ECDC13246588A7D22D3364" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_69B7339380242F32FFB288A7D22D956D" xlink:to="loc_us-gaap_MinorityInterestInLimitedPartnerships_61E08AD0E2ECDC13246588A7D22D3364" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_4A9799300A06A282E7DB88A7D22DADF2" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_69B7339380242F32FFB288A7D22D956D" xlink:to="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_4A9799300A06A282E7DB88A7D22DADF2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_768E075605A214A637CD88A7D22D72DF" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_69B7339380242F32FFB288A7D22D956D" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_768E075605A214A637CD88A7D22D72DF" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_0EFA52B286516606E2833A0B45864C07" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_36AE6CA72AD1BA37593D3A0B458635E5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_0EFA52B286516606E2833A0B45864C07" xlink:to="loc_us-gaap_StatementTable_36AE6CA72AD1BA37593D3A0B458635E5" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_69D3B41FA016EE583EEB3A0B45869DCE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_36AE6CA72AD1BA37593D3A0B458635E5" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_69D3B41FA016EE583EEB3A0B45869DCE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A91DCF1D301B4526F7B03A0B4586A4BC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_69D3B41FA016EE583EEB3A0B45869DCE" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A91DCF1D301B4526F7B03A0B4586A4BC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A91DCF1D301B4526F7B03A0B4586A4BC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_69D3B41FA016EE583EEB3A0B45869DCE" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A91DCF1D301B4526F7B03A0B4586A4BC" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_8062D23648E38A31F9DE3A0B45869446" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A91DCF1D301B4526F7B03A0B4586A4BC" xlink:to="loc_wlkp_CommonUnitsMember_8062D23648E38A31F9DE3A0B45869446" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_DB02B5480D0E5ECD32233A0B4586E391" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A91DCF1D301B4526F7B03A0B4586A4BC" xlink:to="loc_wlkp_SubordinatedUnitsMember_DB02B5480D0E5ECD32233A0B4586E391" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_E4CCE93AE82ADA2C1FC73A0B458645FF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_36AE6CA72AD1BA37593D3A0B458635E5" xlink:to="loc_srt_CounterpartyNameAxis_E4CCE93AE82ADA2C1FC73A0B458645FF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_699C4056AE40CF0877803A0B45862D8D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_E4CCE93AE82ADA2C1FC73A0B458645FF" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_699C4056AE40CF0877803A0B45862D8D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_699C4056AE40CF0877803A0B45862D8D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_E4CCE93AE82ADA2C1FC73A0B458645FF" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_699C4056AE40CF0877803A0B45862D8D" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_UnidentifiedThirdPartiesMember" xlink:label="loc_wlkp_UnidentifiedThirdPartiesMember_A3128A0EC9E6ABCEA1673A0B458611D1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_699C4056AE40CF0877803A0B45862D8D" xlink:to="loc_wlkp_UnidentifiedThirdPartiesMember_A3128A0EC9E6ABCEA1673A0B458611D1" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_AA80B18FABA8BDB377553A0B4586B7DF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_699C4056AE40CF0877803A0B45862D8D" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_AA80B18FABA8BDB377553A0B4586B7DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsIssued" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsIssued_4DDC647746F0820E246F3A0B458671B1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0EFA52B286516606E2833A0B45864C07" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsIssued_4DDC647746F0820E246F3A0B458671B1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_DEAC06F4CAC801E732243A0B45860DAA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_0EFA52B286516606E2833A0B45864C07" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_DEAC06F4CAC801E732243A0B45860DAA" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_7FECCBF0DA3AC4D13AACAD3CC9F34356" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_8A21B5487FEAAD80DF16AD3CC9EF48CE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_7FECCBF0DA3AC4D13AACAD3CC9F34356" xlink:to="loc_us-gaap_StatementTable_8A21B5487FEAAD80DF16AD3CC9EF48CE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_1873E62A98D7C0CE43D8AD3CC9EFDA40" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8A21B5487FEAAD80DF16AD3CC9EF48CE" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_1873E62A98D7C0CE43D8AD3CC9EFDA40" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F9728B7D29AC37103BAAAD3CC9F0BC88_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_1873E62A98D7C0CE43D8AD3CC9EFDA40" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F9728B7D29AC37103BAAAD3CC9F0BC88_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F9728B7D29AC37103BAAAD3CC9F0BC88" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_1873E62A98D7C0CE43D8AD3CC9EFDA40" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F9728B7D29AC37103BAAAD3CC9F0BC88" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_257D81C473378F4957A2AD3CC9F077CE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F9728B7D29AC37103BAAAD3CC9F0BC88" xlink:to="loc_wlkp_CommonUnitsMember_257D81C473378F4957A2AD3CC9F077CE" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_A798BE63A2CE074EA330AD3CC9F0FD41" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_F9728B7D29AC37103BAAAD3CC9F0BC88" xlink:to="loc_wlkp_SubordinatedUnitsMember_A798BE63A2CE074EA330AD3CC9F0FD41" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_F0B2763103D0F1BEECBAAD3CC9F01E03" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8A21B5487FEAAD80DF16AD3CC9EF48CE" xlink:to="loc_srt_CounterpartyNameAxis_F0B2763103D0F1BEECBAAD3CC9F01E03" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6771ED44D84F27E5903FAD3CC9F0A855_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_F0B2763103D0F1BEECBAAD3CC9F01E03" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6771ED44D84F27E5903FAD3CC9F0A855_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6771ED44D84F27E5903FAD3CC9F0A855" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_F0B2763103D0F1BEECBAAD3CC9F01E03" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6771ED44D84F27E5903FAD3CC9F0A855" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_UnidentifiedThirdPartiesMember" xlink:label="loc_wlkp_UnidentifiedThirdPartiesMember_3AF90416E0EBCDB5E941AD3CC9F129F0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6771ED44D84F27E5903FAD3CC9F0A855" xlink:to="loc_wlkp_UnidentifiedThirdPartiesMember_3AF90416E0EBCDB5E941AD3CC9F129F0" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_16FDD376F644937FD674AD3CC9F1F9AC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6771ED44D84F27E5903FAD3CC9F0A855" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_16FDD376F644937FD674AD3CC9F1F9AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_CF7290A27AC2DF871826AD3CC9F108D9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8A21B5487FEAAD80DF16AD3CC9EF48CE" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_CF7290A27AC2DF871826AD3CC9F108D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_AC684608189163EA044CAD3CC9F14631_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_CF7290A27AC2DF871826AD3CC9F108D9" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_AC684608189163EA044CAD3CC9F14631_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_AC684608189163EA044CAD3CC9F14631" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_CF7290A27AC2DF871826AD3CC9F108D9" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_AC684608189163EA044CAD3CC9F14631" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_CB4E4CCA84A36F06BDEBAD3CC9F28CAC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_AC684608189163EA044CAD3CC9F14631" xlink:to="loc_us-gaap_LimitedPartnerMember_CB4E4CCA84A36F06BDEBAD3CC9F28CAC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GeneralPartnerMember" xlink:label="loc_us-gaap_GeneralPartnerMember_66097375BE738051B11FAD3CC9F2326B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_AC684608189163EA044CAD3CC9F14631" xlink:to="loc_us-gaap_GeneralPartnerMember_66097375BE738051B11FAD3CC9F2326B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_76B0610C11481746680AAD3CC9F29991" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8A21B5487FEAAD80DF16AD3CC9EF48CE" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_76B0610C11481746680AAD3CC9F29991" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_73A6F2D2B129D61922BFAD3CC9F20A56_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_76B0610C11481746680AAD3CC9F29991" xlink:to="loc_us-gaap_EquityComponentDomain_73A6F2D2B129D61922BFAD3CC9F20A56_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_73A6F2D2B129D61922BFAD3CC9F20A56" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_76B0610C11481746680AAD3CC9F29991" xlink:to="loc_us-gaap_EquityComponentDomain_73A6F2D2B129D61922BFAD3CC9F20A56" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_67E2EA56BF0CCF57617CAD3CC9F3C787" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_73A6F2D2B129D61922BFAD3CC9F20A56" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_67E2EA56BF0CCF57617CAD3CC9F3C787" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="loc_us-gaap_NoncontrollingInterestMember_F29B84849664968F881EAD3CC9F3FEFF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_73A6F2D2B129D61922BFAD3CC9F20A56" xlink:to="loc_us-gaap_NoncontrollingInterestMember_F29B84849664968F881EAD3CC9F3FEFF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_2D6BC65B2FCEA8CF9C15AD3CC9F394B4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7FECCBF0DA3AC4D13AACAD3CC9F34356" xlink:to="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_2D6BC65B2FCEA8CF9C15AD3CC9F394B4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_02D1F95972FC174E030AAD3CC9F4840B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7FECCBF0DA3AC4D13AACAD3CC9F34356" xlink:to="loc_us-gaap_ProfitLoss_02D1F95972FC174E030AAD3CC9F4840B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax_38CA283133DFCDCD5636AD3CC9F40DC9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7FECCBF0DA3AC4D13AACAD3CC9F34356" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax_38CA283133DFCDCD5636AD3CC9F40DC9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity" xlink:label="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_32BC707875846ADC9C6DAD3CC9F440CD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7FECCBF0DA3AC4D13AACAD3CC9F34356" xlink:to="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_32BC707875846ADC9C6DAD3CC9F440CD" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ConversionofUnitsAmount" xlink:label="loc_wlkp_ConversionofUnitsAmount_850ACBC3BD6EAF2AB358AD3CC9F4D397" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7FECCBF0DA3AC4D13AACAD3CC9F34356" xlink:to="loc_wlkp_ConversionofUnitsAmount_850ACBC3BD6EAF2AB358AD3CC9F4D397" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationGross" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationGross_7C50D9E748DA5894DD25AD3CC9F41CEF" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7FECCBF0DA3AC4D13AACAD3CC9F34356" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationGross_7C50D9E748DA5894DD25AD3CC9F41CEF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountDistributionAmount" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountDistributionAmount_CD00BA0228A33D554588AD3CC9F4799E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7FECCBF0DA3AC4D13AACAD3CC9F34356" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountDistributionAmount_CD00BA0228A33D554588AD3CC9F4799E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_7BC69781476E2FB54BAFAD3CC9F5F1C7" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7FECCBF0DA3AC4D13AACAD3CC9F34356" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_7BC69781476E2FB54BAFAD3CC9F5F1C7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/ConsolidatedStatementsOfOperations" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_AC93A4CBD781DB7A7EFFAD3CC9FC451E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_StatementTable_AC93A4CBD781DB7A7EFFAD3CC9FC451E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srt_ProductOrServiceAxis_78671B6525679CEA7FDBAD3CC9FCC5C1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_AC93A4CBD781DB7A7EFFAD3CC9FC451E" xlink:to="loc_srt_ProductOrServiceAxis_78671B6525679CEA7FDBAD3CC9FCC5C1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_8C68FAD8A6834CC46B5AAD3CC9FDF2AB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_78671B6525679CEA7FDBAD3CC9FCC5C1" xlink:to="loc_srt_ProductsAndServicesDomain_8C68FAD8A6834CC46B5AAD3CC9FDF2AB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_8C68FAD8A6834CC46B5AAD3CC9FDF2AB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_78671B6525679CEA7FDBAD3CC9FCC5C1" xlink:to="loc_srt_ProductsAndServicesDomain_8C68FAD8A6834CC46B5AAD3CC9FDF2AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProductAndServiceOtherMember" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_580F0C368ABBA4173D04AD3CC9FD444D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_8C68FAD8A6834CC46B5AAD3CC9FDF2AB" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_580F0C368ABBA4173D04AD3CC9FD444D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_CD4DAC713C6F0B30AC97AD3CC9FEAE00" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_AC93A4CBD781DB7A7EFFAD3CC9FC451E" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_CD4DAC713C6F0B30AC97AD3CC9FEAE00" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B68F2324D4EA24832EABAD3CC9FE21D8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_CD4DAC713C6F0B30AC97AD3CC9FEAE00" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B68F2324D4EA24832EABAD3CC9FE21D8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B68F2324D4EA24832EABAD3CC9FE21D8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_CD4DAC713C6F0B30AC97AD3CC9FEAE00" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B68F2324D4EA24832EABAD3CC9FE21D8" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_86AA30CCE77E98DEC8BCAD3CC9FEDFAA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B68F2324D4EA24832EABAD3CC9FE21D8" xlink:to="loc_wlkp_CommonUnitsMember_86AA30CCE77E98DEC8BCAD3CC9FEDFAA" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_71B48F46A73CA089F97EAD3CC9FE8379" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_B68F2324D4EA24832EABAD3CC9FE21D8" xlink:to="loc_wlkp_SubordinatedUnitsMember_71B48F46A73CA089F97EAD3CC9FE8379" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_27E15036F71390A7D801AD3CC9FF9230" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_AC93A4CBD781DB7A7EFFAD3CC9FC451E" xlink:to="loc_srt_CounterpartyNameAxis_27E15036F71390A7D801AD3CC9FF9230" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_531D484A2003FC361AD8AD3CC9FFCD48_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_27E15036F71390A7D801AD3CC9FF9230" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_531D484A2003FC361AD8AD3CC9FFCD48_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_531D484A2003FC361AD8AD3CC9FFCD48" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_27E15036F71390A7D801AD3CC9FF9230" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_531D484A2003FC361AD8AD3CC9FFCD48" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_UnidentifiedThirdPartiesMember" xlink:label="loc_wlkp_UnidentifiedThirdPartiesMember_8CE549AC362A09B963C4AD3CC9FFC035" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_531D484A2003FC361AD8AD3CC9FFCD48" xlink:to="loc_wlkp_UnidentifiedThirdPartiesMember_8CE549AC362A09B963C4AD3CC9FFC035" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_9BAD201C843A1CAE35F9AD3CC9FF7648" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_531D484A2003FC361AD8AD3CC9FFCD48" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_9BAD201C843A1CAE35F9AD3CC9FF7648" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueFromRelatedParties" xlink:label="loc_us-gaap_RevenueFromRelatedParties_E53B90B0BE3538058020AD4951D9E650" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_RevenueFromRelatedParties_E53B90B0BE3538058020AD4951D9E650" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_F4D47FAB523C46B621D4AD3CCA00B174" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_Revenues_F4D47FAB523C46B621D4AD3CCA00B174" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CostOfGoodsAndServicesSold" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_F0AA5E7A3584A00FB235AD3CCA000F02" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_F0AA5E7A3584A00FB235AD3CCA000F02" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GrossProfit" xlink:label="loc_us-gaap_GrossProfit_1291AB2A911E3F89EC11AD3CCA006CBB" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_GrossProfit_1291AB2A911E3F89EC11AD3CCA006CBB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_6C21FAA5060439E92E58AD3CCA00D468" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_6C21FAA5060439E92E58AD3CCA00D468" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_7A7D1CE17E1ECEAB3515AD3CCA018B0C" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_OperatingIncomeLoss_7A7D1CE17E1ECEAB3515AD3CCA018B0C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NonoperatingIncomeExpenseAbstract" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_77750D53CA24CB7C80F4AD3CCA0190E7" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_77750D53CA24CB7C80F4AD3CCA0190E7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestExpenseRelatedParty" xlink:label="loc_us-gaap_InterestExpenseRelatedParty_0957A01DF0B9EA8050A0AD3CCA01C9AB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_77750D53CA24CB7C80F4AD3CCA0190E7" xlink:to="loc_us-gaap_InterestExpenseRelatedParty_0957A01DF0B9EA8050A0AD3CCA01C9AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_130EEB0D755B21D82E4CAD3CCA014899" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_77750D53CA24CB7C80F4AD3CCA0190E7" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_130EEB0D755B21D82E4CAD3CCA014899" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_73FB22CD9BB98EC2A752AD3CCA01352C" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_73FB22CD9BB98EC2A752AD3CCA01352C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_68409B129C7ECA0D3CE6AD3CCA02D417" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_68409B129C7ECA0D3CE6AD3CCA02D417" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_1F6D903B9ED16039EB2DAD3CCA0202B3" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_ProfitLoss_1F6D903B9ED16039EB2DAD3CCA0202B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_DBC25937786EEF22A634AD3CCA02AB98" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_DBC25937786EEF22A634AD3CCA02AB98" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_EEFBFE5409F79EF781D1AD3CCA028DCF" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_NetIncomeLoss_EEFBFE5409F79EF781D1AD3CCA028DCF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_30B6A6E01F163C391847AD3CCA02ACF4" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_30B6A6E01F163C391847AD3CCA02ACF4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDiluted_63E5185D809EBDEC24C9AD3CCA0342E5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_30B6A6E01F163C391847AD3CCA02ACF4" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDiluted_63E5185D809EBDEC24C9AD3CCA0342E5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_E9B83C0EEC6F3C00A5C3AD3CCA03A277" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_89E62B65B1BF4C4A12B1AD3CCA00C5F0" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_E9B83C0EEC6F3C00A5C3AD3CCA03A277" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:label="loc_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_5CB7E8D20CAA0AE8532FAD3CCA034B1D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_E9B83C0EEC6F3C00A5C3AD3CCA03A277" xlink:to="loc_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_5CB7E8D20CAA0AE8532FAD3CCA034B1D" xlink:type="arc" />
  </link:definitionLink>
  <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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountLineItems" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_6BB3F2B9AE79193390023A0B45C474C7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable" xlink:label="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_32CA30BE0FA48289B2EB3A0B45B50742" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_6BB3F2B9AE79193390023A0B45C474C7" xlink:to="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_32CA30BE0FA48289B2EB3A0B45B50742" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_36CD0F6A93FA77A61A143A0B45B58549" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_32CA30BE0FA48289B2EB3A0B45B50742" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_36CD0F6A93FA77A61A143A0B45B58549" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_167941A1B611CF49F5C63A0B45B53738_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_36CD0F6A93FA77A61A143A0B45B58549" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_167941A1B611CF49F5C63A0B45B53738_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_167941A1B611CF49F5C63A0B45B53738" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_36CD0F6A93FA77A61A143A0B45B58549" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_167941A1B611CF49F5C63A0B45B53738" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_FCA842A6B33D0E2B9EA03A0B45B5E9DF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_167941A1B611CF49F5C63A0B45B53738" xlink:to="loc_us-gaap_LimitedPartnerMember_FCA842A6B33D0E2B9EA03A0B45B5E9DF" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_BB6783EA1D31887D6DB73A0B45B54CD3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_32CA30BE0FA48289B2EB3A0B45B50742" xlink:to="loc_dei_LegalEntityAxis_BB6783EA1D31887D6DB73A0B45B54CD3" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_3B35038D87CA3EC8EF5C3A0B45B57C93_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_BB6783EA1D31887D6DB73A0B45B54CD3" xlink:to="loc_dei_EntityDomain_3B35038D87CA3EC8EF5C3A0B45B57C93_default" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_3B35038D87CA3EC8EF5C3A0B45B57C93" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_BB6783EA1D31887D6DB73A0B45B54CD3" xlink:to="loc_dei_EntityDomain_3B35038D87CA3EC8EF5C3A0B45B57C93" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_B6D137004879A3EC87E13A0B45B56E8C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_3B35038D87CA3EC8EF5C3A0B45B57C93" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_B6D137004879A3EC87E13A0B45B56E8C" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_WestlakeChemicalOpCoLPMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoLPMember_EA9EC96F57E993F87C1B3A0B45B5E2DF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_3B35038D87CA3EC8EF5C3A0B45B57C93" xlink:to="loc_wlkp_WestlakeChemicalOpCoLPMember_EA9EC96F57E993F87C1B3A0B45B5E2DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_8C483C3534583D3B16463A0B45B57F8C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_32CA30BE0FA48289B2EB3A0B45B50742" xlink:to="loc_srt_CounterpartyNameAxis_8C483C3534583D3B16463A0B45B57F8C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_465F7526F3728BAA79043A0B45B53232_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_8C483C3534583D3B16463A0B45B57F8C" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_465F7526F3728BAA79043A0B45B53232_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_465F7526F3728BAA79043A0B45B53232" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_8C483C3534583D3B16463A0B45B57F8C" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_465F7526F3728BAA79043A0B45B53232" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_593108E88D3BD7B722353A0B45B56AC2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_465F7526F3728BAA79043A0B45B53232" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_593108E88D3BD7B722353A0B45B56AC2" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_WestlakeChemicalOpCoLPMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoLPMember_4E796E037124FD65C1193A0B45B5DCC7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_465F7526F3728BAA79043A0B45B53232" xlink:to="loc_wlkp_WestlakeChemicalOpCoLPMember_4E796E037124FD65C1193A0B45B5DCC7" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_WestlakeChemicalOpCoGPLLCMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoGPLLCMember_A13A34E6B94D3EB19FC73A0B45B59425" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_465F7526F3728BAA79043A0B45B53232" xlink:to="loc_wlkp_WestlakeChemicalOpCoGPLLCMember_A13A34E6B94D3EB19FC73A0B45B59425" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2E5A3E2D43BB381F91043A0B45B50B18" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_32CA30BE0FA48289B2EB3A0B45B50742" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2E5A3E2D43BB381F91043A0B45B50B18" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_A6360FB1E44DE7ABD7353A0B45B593CB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2E5A3E2D43BB381F91043A0B45B50B18" xlink:to="loc_us-gaap_RelatedPartyDomain_A6360FB1E44DE7ABD7353A0B45B593CB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_A6360FB1E44DE7ABD7353A0B45B593CB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_2E5A3E2D43BB381F91043A0B45B50B18" xlink:to="loc_us-gaap_RelatedPartyDomain_A6360FB1E44DE7ABD7353A0B45B593CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_AffiliatedEntityMember" xlink:label="loc_srt_AffiliatedEntityMember_9A80B8B32D25343563973A0B45B53057" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_A6360FB1E44DE7ABD7353A0B45B593CB" xlink:to="loc_srt_AffiliatedEntityMember_9A80B8B32D25343563973A0B45B53057" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_WestlakeChemicalOpCoLPMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoLPMember_8F7E0E4326CD7B24A8FA3A0B45C40639" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_A6360FB1E44DE7ABD7353A0B45B593CB" xlink:to="loc_wlkp_WestlakeChemicalOpCoLPMember_8F7E0E4326CD7B24A8FA3A0B45C40639" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedLiabilityCompanyMember" xlink:label="loc_us-gaap_LimitedLiabilityCompanyMember_FF8BF39809C1DCF89CA73A0B45C43174" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_A6360FB1E44DE7ABD7353A0B45B593CB" xlink:to="loc_us-gaap_LimitedLiabilityCompanyMember_FF8BF39809C1DCF89CA73A0B45C43174" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MajorityOwnedSubsidiaryUnconsolidatedMember" xlink:label="loc_us-gaap_MajorityOwnedSubsidiaryUnconsolidatedMember_0B33E96FDF5CB47EC73A3A0B45C4C07F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_A6360FB1E44DE7ABD7353A0B45B593CB" xlink:to="loc_us-gaap_MajorityOwnedSubsidiaryUnconsolidatedMember_0B33E96FDF5CB47EC73A3A0B45C4C07F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering" xlink:label="loc_us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering_EB5927FF763F3059E1733A0B45C4E1BD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_6BB3F2B9AE79193390023A0B45C474C7" xlink:to="loc_us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering_EB5927FF763F3059E1733A0B45C4E1BD" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit" xlink:label="loc_wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit_F5E7EA25D26338E112813A0B45C43FBD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_6BB3F2B9AE79193390023A0B45C474C7" xlink:to="loc_wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit_F5E7EA25D26338E112813A0B45C43FBD" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity" xlink:label="loc_wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity_C04AAEF9CB99CB700E3F3A0B45C4C706" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_6BB3F2B9AE79193390023A0B45C474C7" xlink:to="loc_wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity_C04AAEF9CB99CB700E3F3A0B45C4C706" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest" xlink:label="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest_5BCF44E38D927B1978CB3A0B45C4AD3F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_6BB3F2B9AE79193390023A0B45C474C7" xlink:to="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest_5BCF44E38D927B1978CB3A0B45C4AD3F" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_LimitedLiabilityCompanyLLCorLimitedPartnershipLPMembersorLimitedPartnersAdditionalOwnershipInterest" xlink:label="loc_wlkp_LimitedLiabilityCompanyLLCorLimitedPartnershipLPMembersorLimitedPartnersAdditionalOwnershipInterest_D45105455DE79415F1013A0B45C4EC39" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_6BB3F2B9AE79193390023A0B45C474C7" xlink:to="loc_wlkp_LimitedLiabilityCompanyLLCorLimitedPartnershipLPMembersorLimitedPartnersAdditionalOwnershipInterest_D45105455DE79415F1013A0B45C4EC39" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsToAcquireLimitedPartnershipInterests" xlink:label="loc_us-gaap_PaymentsToAcquireLimitedPartnershipInterests_3FE6D7AEC1F3672633493A0B45C41DF2" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_6BB3F2B9AE79193390023A0B45C474C7" xlink:to="loc_us-gaap_PaymentsToAcquireLimitedPartnershipInterests_3FE6D7AEC1F3672633493A0B45C41DF2" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_NumberofProductionFacilities" xlink:label="loc_wlkp_NumberofProductionFacilities_51BF5199F34411BCB6153A0B45C4F78F" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_6BB3F2B9AE79193390023A0B45C474C7" xlink:to="loc_wlkp_NumberofProductionFacilities_51BF5199F34411BCB6153A0B45C4F78F" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountLineItems" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_8C2D09A54F67A1ACB93888A7D190D56A" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable" xlink:label="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_0977311321C88D4FB10A88A7D190ACF6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_8C2D09A54F67A1ACB93888A7D190D56A" xlink:to="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_0977311321C88D4FB10A88A7D190ACF6" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_69B6D34A5BBEE37ABB3588A7D1907C05" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_0977311321C88D4FB10A88A7D190ACF6" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_69B6D34A5BBEE37ABB3588A7D1907C05" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_8FCBAD2F2CBA0C3F67D288A7D1904863_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_69B6D34A5BBEE37ABB3588A7D1907C05" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_8FCBAD2F2CBA0C3F67D288A7D1904863_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_8FCBAD2F2CBA0C3F67D288A7D1904863" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_69B6D34A5BBEE37ABB3588A7D1907C05" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_8FCBAD2F2CBA0C3F67D288A7D1904863" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_6C111D1CB12461E03BBB88A7D1905588" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_8FCBAD2F2CBA0C3F67D288A7D1904863" xlink:to="loc_wlkp_IDRHoldersMember_6C111D1CB12461E03BBB88A7D1905588" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_7BB0A1BAE69EA05BEC5F88A7D190F723" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLimitedPartnersCapitalAccountByClassTable_0977311321C88D4FB10A88A7D190ACF6" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_7BB0A1BAE69EA05BEC5F88A7D190F723" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A25BCAF006C10D9FEF1488A7D190E607_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_7BB0A1BAE69EA05BEC5F88A7D190F723" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A25BCAF006C10D9FEF1488A7D190E607_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A25BCAF006C10D9FEF1488A7D190E607" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_7BB0A1BAE69EA05BEC5F88A7D190F723" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A25BCAF006C10D9FEF1488A7D190E607" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_19702D40AC026DF2C3C088A7D1903A5C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A25BCAF006C10D9FEF1488A7D190E607" xlink:to="loc_wlkp_CommonUnitsMember_19702D40AC026DF2C3C088A7D1903A5C" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_C328CC7D40D3C014424588A7D1907408" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_A25BCAF006C10D9FEF1488A7D190E607" xlink:to="loc_wlkp_SubordinatedUnitsMember_C328CC7D40D3C014424588A7D1907408" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributedEarnings" xlink:label="loc_us-gaap_DistributedEarnings_0F4E9C74B9186ED7594688A7D1900EEB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_8C2D09A54F67A1ACB93888A7D190D56A" xlink:to="loc_us-gaap_DistributedEarnings_0F4E9C74B9186ED7594688A7D1900EEB" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IncentiveDistributionSubsequentDistributionAmount" xlink:label="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_8679F59EAA3C0B49CBC888A7D190B84B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_8C2D09A54F67A1ACB93888A7D190D56A" xlink:to="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_8679F59EAA3C0B49CBC888A7D190B84B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UndistributedEarnings" xlink:label="loc_us-gaap_UndistributedEarnings_AE18775F396E78916AD588A7D190C702" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_8C2D09A54F67A1ACB93888A7D190D56A" xlink:to="loc_us-gaap_UndistributedEarnings_AE18775F396E78916AD588A7D190C702" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_3ABCCCC57CB5A58ACF0188A7D19004F9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_8C2D09A54F67A1ACB93888A7D190D56A" xlink:to="loc_us-gaap_NetIncomeLoss_3ABCCCC57CB5A58ACF0188A7D19004F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_773BC742B2C7A93330BE88A7D190B822" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_8C2D09A54F67A1ACB93888A7D190D56A" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_773BC742B2C7A93330BE88A7D190B822" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:label="loc_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_BA80728159232AEC7BE688A7D190FB5B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_773BC742B2C7A93330BE88A7D190B822" xlink:to="loc_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_BA80728159232AEC7BE688A7D190FB5B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_68343A7A568D7B48234E88A7D190C54E" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountLineItems_8C2D09A54F67A1ACB93888A7D190D56A" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_68343A7A568D7B48234E88A7D190C54E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDiluted_C495146F9FF9EB8591D588A7D1907A8C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_68343A7A568D7B48234E88A7D190C54E" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDiluted_C495146F9FF9EB8591D588A7D1907A8C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitDistributionPerCommonUnitDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/DistributionsAndNetIncomePerLimitedPartnerUnitDistributionsDeclaredDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionMadeToLimitedPartnerLineItems" xlink:label="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionsMadeToLimitedPartnerTable" xlink:label="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_4864121CE7D6BA2DCA9688A7D1A0C0D4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_4864121CE7D6BA2DCA9688A7D1A0C0D4" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis" xlink:label="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_C73C653A6CE5DCF9EF8588A7D1A00D50" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_4864121CE7D6BA2DCA9688A7D1A0C0D4" xlink:to="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_C73C653A6CE5DCF9EF8588A7D1A00D50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_49EB69220BA42685B90588A7D1A02F30_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_C73C653A6CE5DCF9EF8588A7D1A00D50" xlink:to="loc_us-gaap_DistributionTypeDomain_49EB69220BA42685B90588A7D1A02F30_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_49EB69220BA42685B90588A7D1A02F30" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_C73C653A6CE5DCF9EF8588A7D1A00D50" xlink:to="loc_us-gaap_DistributionTypeDomain_49EB69220BA42685B90588A7D1A02F30" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashDistributionMember" xlink:label="loc_us-gaap_CashDistributionMember_62CD766228C222D229ED88A7D1A04B60" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionTypeDomain_49EB69220BA42685B90588A7D1A02F30" xlink:to="loc_us-gaap_CashDistributionMember_62CD766228C222D229ED88A7D1A04B60" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CashDistributionTrancheOneMember" xlink:label="loc_wlkp_CashDistributionTrancheOneMember_5497B927435E732E492588A7D1A0E9C6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashDistributionMember_62CD766228C222D229ED88A7D1A04B60" xlink:to="loc_wlkp_CashDistributionTrancheOneMember_5497B927435E732E492588A7D1A0E9C6" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CashDistributionTrancheTwoMember" xlink:label="loc_wlkp_CashDistributionTrancheTwoMember_101A22B869607DD85A5088A7D1A054AD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashDistributionMember_62CD766228C222D229ED88A7D1A04B60" xlink:to="loc_wlkp_CashDistributionTrancheTwoMember_101A22B869607DD85A5088A7D1A054AD" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CashDistributionTrancheThreeMember" xlink:label="loc_wlkp_CashDistributionTrancheThreeMember_5534A53B80D8E2C0665488A7D1A0B9F2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionTypeDomain_49EB69220BA42685B90588A7D1A02F30" xlink:to="loc_wlkp_CashDistributionTrancheThreeMember_5534A53B80D8E2C0665488A7D1A0B9F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_37505531C05F875B028A88A7D1A0F30B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_4864121CE7D6BA2DCA9688A7D1A0C0D4" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_37505531C05F875B028A88A7D1A0F30B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BA2689F0864EE6EFAE3D88A7D1A07494_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_37505531C05F875B028A88A7D1A0F30B" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BA2689F0864EE6EFAE3D88A7D1A07494_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BA2689F0864EE6EFAE3D88A7D1A07494" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_37505531C05F875B028A88A7D1A0F30B" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BA2689F0864EE6EFAE3D88A7D1A07494" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_0921C04F6C1CFDBCF58D88A7D1A0B272" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BA2689F0864EE6EFAE3D88A7D1A07494" xlink:to="loc_wlkp_CommonUnitsMember_0921C04F6C1CFDBCF58D88A7D1A0B272" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_D50FA6360139B4367B3388A7D1A0CD55" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BA2689F0864EE6EFAE3D88A7D1A07494" xlink:to="loc_wlkp_SubordinatedUnitsMember_D50FA6360139B4367B3388A7D1A0CD55" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CommonAndSubordinatedUnitsMember" xlink:label="loc_wlkp_CommonAndSubordinatedUnitsMember_76B832BA4ABEE941984D88A7D1A035BD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_BA2689F0864EE6EFAE3D88A7D1A07494" xlink:to="loc_wlkp_CommonAndSubordinatedUnitsMember_76B832BA4ABEE941984D88A7D1A035BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_E121C0ABA7BD050C5D4688A7D1A038C7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_4864121CE7D6BA2DCA9688A7D1A0C0D4" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_E121C0ABA7BD050C5D4688A7D1A038C7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_46AE98F6A265D18DD73188A7D1A06FD3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_E121C0ABA7BD050C5D4688A7D1A038C7" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_46AE98F6A265D18DD73188A7D1A06FD3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_46AE98F6A265D18DD73188A7D1A06FD3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_E121C0ABA7BD050C5D4688A7D1A038C7" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_46AE98F6A265D18DD73188A7D1A06FD3" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_UnitHoldersMember" xlink:label="loc_wlkp_UnitHoldersMember_E2DA31F33F0797E4401488A7D1A0D4E4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_46AE98F6A265D18DD73188A7D1A06FD3" xlink:to="loc_wlkp_UnitHoldersMember_E2DA31F33F0797E4401488A7D1A0D4E4" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_DD7542122DD7DE02A46A88A7D1A0BB3C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_46AE98F6A265D18DD73188A7D1A06FD3" xlink:to="loc_wlkp_IDRHoldersMember_DD7542122DD7DE02A46A88A7D1A0BB3C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_B696E2E3CF736C5D156088A7D1A0E3A9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_4864121CE7D6BA2DCA9688A7D1A0C0D4" xlink:to="loc_srt_CounterpartyNameAxis_B696E2E3CF736C5D156088A7D1A0E3A9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_04C3277CF60CA195427C88A7D1A033D8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_B696E2E3CF736C5D156088A7D1A0E3A9" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_04C3277CF60CA195427C88A7D1A033D8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_04C3277CF60CA195427C88A7D1A033D8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_B696E2E3CF736C5D156088A7D1A0E3A9" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_04C3277CF60CA195427C88A7D1A033D8" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_1F8EB3AB766901559F5888A7D1A0C30A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_04C3277CF60CA195427C88A7D1A033D8" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_1F8EB3AB766901559F5888A7D1A0C30A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_70371B2DAD4877AC6AD288A7D1A0C1BC" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_4864121CE7D6BA2DCA9688A7D1A0C0D4" xlink:to="loc_srt_RangeAxis_70371B2DAD4877AC6AD288A7D1A0C1BC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_CD5F9F1C501544F8602588A7D1A08BDE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_70371B2DAD4877AC6AD288A7D1A0C1BC" xlink:to="loc_srt_RangeMember_CD5F9F1C501544F8602588A7D1A08BDE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_CD5F9F1C501544F8602588A7D1A08BDE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_70371B2DAD4877AC6AD288A7D1A0C1BC" xlink:to="loc_srt_RangeMember_CD5F9F1C501544F8602588A7D1A08BDE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_084CD4B2D910A00B1DB588A7D1A0AD2A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_CD5F9F1C501544F8602588A7D1A08BDE" xlink:to="loc_srt_MinimumMember_084CD4B2D910A00B1DB588A7D1A0AD2A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_04147E698A6C60C7EE3E88A7D1A022CE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_CD5F9F1C501544F8602588A7D1A08BDE" xlink:to="loc_srt_MaximumMember_04147E698A6C60C7EE3E88A7D1A022CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_B018332D61AF27AFFEC588A7D1A031FA" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DistributionsMadeToLimitedPartnerTable_4864121CE7D6BA2DCA9688A7D1A0C0D4" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_B018332D61AF27AFFEC588A7D1A031FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_9F0C84C14BE42189DAC788A7D1A00CA3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_B018332D61AF27AFFEC588A7D1A031FA" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_9F0C84C14BE42189DAC788A7D1A00CA3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_9F0C84C14BE42189DAC788A7D1A00CA3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_B018332D61AF27AFFEC588A7D1A031FA" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_9F0C84C14BE42189DAC788A7D1A00CA3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_5AF967067F6C24BC905A88A7D1A01294" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_9F0C84C14BE42189DAC788A7D1A00CA3" xlink:to="loc_us-gaap_SubsequentEventMember_5AF967067F6C24BC905A88A7D1A01294" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit" xlink:label="loc_us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit_ED4A6C7FE8E536D53B4088A7D1A0FF49" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit_ED4A6C7FE8E536D53B4088A7D1A0FF49" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IncentiveDistributionMarginalPercentageInterestinDistributions" xlink:label="loc_wlkp_IncentiveDistributionMarginalPercentageInterestinDistributions_3728A8D34864BFE01C0488A7D1A097CD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_wlkp_IncentiveDistributionMarginalPercentageInterestinDistributions_3728A8D34864BFE01C0488A7D1A097CD" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IncentiveDistributionRightsTargetDistributionPerUnitRequiringMarginalPercentageDistributiontoIDRHolders" xlink:label="loc_wlkp_IncentiveDistributionRightsTargetDistributionPerUnitRequiringMarginalPercentageDistributiontoIDRHolders_C72EA6C72C191E8128D288A7D1A0916B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_wlkp_IncentiveDistributionRightsTargetDistributionPerUnitRequiringMarginalPercentageDistributiontoIDRHolders_C72EA6C72C191E8128D288A7D1A0916B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_BEB88DBCB4350BA1064B88A7D1A06270" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_us-gaap_NetIncomeLoss_BEB88DBCB4350BA1064B88A7D1A06270" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributedEarnings" xlink:label="loc_us-gaap_DistributedEarnings_732CEC2DFA2928CF28E888A7D1A01FA9" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_us-gaap_DistributedEarnings_732CEC2DFA2928CF28E888A7D1A01FA9" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IncentiveDistributionSubsequentDistributionAmount" xlink:label="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_2042B897D5111345D19388A7D1A09724" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_2042B897D5111345D19388A7D1A09724" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UndistributedEarnings" xlink:label="loc_us-gaap_UndistributedEarnings_D38FDA5165AD5F0FD16D88A7D1A00924" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_us-gaap_UndistributedEarnings_D38FDA5165AD5F0FD16D88A7D1A00924" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IncentiveDistributionQuarterlyDistributionPerUnitDistributionThreshold" xlink:label="loc_wlkp_IncentiveDistributionQuarterlyDistributionPerUnitDistributionThreshold_3330214ABE99E7C7075288A7D1A0FCD0" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_wlkp_IncentiveDistributionQuarterlyDistributionPerUnitDistributionThreshold_3330214ABE99E7C7075288A7D1A0FCD0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:label="loc_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_DAD57D52BD87DE2FC2BE88A7D1A0872E" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_DAD57D52BD87DE2FC2BE88A7D1A0872E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDiluted_5A5CED390FE985F133C788A7D1A01162" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionMadeToLimitedPartnerLineItems_12C3AE06BA11639940CA88A7D1A0EC40" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDiluted_5A5CED390FE985F133C788A7D1A01162" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_9C0378DD3B02E9BBF08B88A7D190B2D1" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable" xlink:label="loc_us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable_07CB63799EB6919ED5F188A7D190550D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_9C0378DD3B02E9BBF08B88A7D190B2D1" xlink:to="loc_us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable_07CB63799EB6919ED5F188A7D190550D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis" xlink:label="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_95F7F8A0DF7EBC06A86A88A7D1904559" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable_07CB63799EB6919ED5F188A7D190550D" xlink:to="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_95F7F8A0DF7EBC06A86A88A7D1904559" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_2649B71E0DB60D60181688A7D1903D6C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_95F7F8A0DF7EBC06A86A88A7D1904559" xlink:to="loc_us-gaap_DistributionTypeDomain_2649B71E0DB60D60181688A7D1903D6C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_2649B71E0DB60D60181688A7D1903D6C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_95F7F8A0DF7EBC06A86A88A7D1904559" xlink:to="loc_us-gaap_DistributionTypeDomain_2649B71E0DB60D60181688A7D1903D6C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashDistributionMember" xlink:label="loc_us-gaap_CashDistributionMember_47782E60636430182EA588A7D1902B29" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionTypeDomain_2649B71E0DB60D60181688A7D1903D6C" xlink:to="loc_us-gaap_CashDistributionMember_47782E60636430182EA588A7D1902B29" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_47C8942865FA9440417988A7D1904AAC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable_07CB63799EB6919ED5F188A7D190550D" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_47C8942865FA9440417988A7D1904AAC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_CD21295556E54F1DA4B888A7D190791B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_47C8942865FA9440417988A7D1904AAC" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_CD21295556E54F1DA4B888A7D190791B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_CD21295556E54F1DA4B888A7D190791B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_47C8942865FA9440417988A7D1904AAC" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_CD21295556E54F1DA4B888A7D190791B" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_E0CF618023B018A44D1688A7D1904C40" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_CD21295556E54F1DA4B888A7D190791B" xlink:to="loc_wlkp_CommonUnitsMember_E0CF618023B018A44D1688A7D1904C40" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_57FA9A5C45B09C0BA93888A7D19085C4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_CD21295556E54F1DA4B888A7D190791B" xlink:to="loc_wlkp_SubordinatedUnitsMember_57FA9A5C45B09C0BA93888A7D19085C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_2F095DB337A3D26E922588A7D190CAE0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIncentiveDistributionMadeToManagingMemberOrGeneralPartnerTable_07CB63799EB6919ED5F188A7D190550D" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_2F095DB337A3D26E922588A7D190CAE0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_CE7305E7BBB82BB7317488A7D190E0FF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_2F095DB337A3D26E922588A7D190CAE0" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_CE7305E7BBB82BB7317488A7D190E0FF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_CE7305E7BBB82BB7317488A7D190E0FF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_2F095DB337A3D26E922588A7D190CAE0" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_CE7305E7BBB82BB7317488A7D190E0FF" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_6D992DE69A7F22E6EA2C88A7D19041F4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_CE7305E7BBB82BB7317488A7D190E0FF" xlink:to="loc_wlkp_IDRHoldersMember_6D992DE69A7F22E6EA2C88A7D19041F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_2A257C5618E5EFD3F96888A7D1908ED5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_9C0378DD3B02E9BBF08B88A7D190B2D1" xlink:to="loc_us-gaap_NetIncomeLoss_2A257C5618E5EFD3F96888A7D1908ED5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributedEarnings" xlink:label="loc_us-gaap_DistributedEarnings_05D4104911B57E0A5DEA88A7D190E638" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_9C0378DD3B02E9BBF08B88A7D190B2D1" xlink:to="loc_us-gaap_DistributedEarnings_05D4104911B57E0A5DEA88A7D190E638" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IncentiveDistributionSubsequentDistributionAmount" xlink:label="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_8B3268A14B7FD352093A88A7D190AAF0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_9C0378DD3B02E9BBF08B88A7D190B2D1" xlink:to="loc_wlkp_IncentiveDistributionSubsequentDistributionAmount_8B3268A14B7FD352093A88A7D190AAF0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UndistributedEarnings" xlink:label="loc_us-gaap_UndistributedEarnings_981CFCD06F9F606CCC1A88A7D1902CEA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerLineItems_9C0378DD3B02E9BBF08B88A7D190B2D1" xlink:to="loc_us-gaap_UndistributedEarnings_981CFCD06F9F606CCC1A88A7D1902CEA" 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="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentInformationLineItems" xlink:label="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:type="locator" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentInformationTable" xlink:label="loc_dei_DocumentInformationTable_6C2DAA5D22EB0AC23597AD3CCA6EB003" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_DocumentInformationTable_6C2DAA5D22EB0AC23597AD3CCA6EB003" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_D29C10B35311EF079E72AD3CCA6EE582" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_6C2DAA5D22EB0AC23597AD3CCA6EB003" xlink:to="loc_us-gaap_StatementClassOfStockAxis_D29C10B35311EF079E72AD3CCA6EE582" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_9B96B0A5E57C52614054AD3CCA6F81DB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_D29C10B35311EF079E72AD3CCA6EE582" xlink:to="loc_us-gaap_ClassOfStockDomain_9B96B0A5E57C52614054AD3CCA6F81DB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_9B96B0A5E57C52614054AD3CCA6F81DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_D29C10B35311EF079E72AD3CCA6EE582" xlink:to="loc_us-gaap_ClassOfStockDomain_9B96B0A5E57C52614054AD3CCA6F81DB" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CommonUnitsMember" xlink:label="loc_wlkp_CommonUnitsMember_720478C87422FEDBB540AD3CCA6F2DD2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_9B96B0A5E57C52614054AD3CCA6F81DB" xlink:to="loc_wlkp_CommonUnitsMember_720478C87422FEDBB540AD3CCA6F2DD2" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentType" xlink:label="loc_dei_DocumentType_D15C0BBC8736924E2DF3AD3CCA6F02F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_DocumentType_D15C0BBC8736924E2DF3AD3CCA6F02F2" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_AmendmentFlag" xlink:label="loc_dei_AmendmentFlag_C22EE926804E5C3555E2AD3CCA6FADCB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_AmendmentFlag_C22EE926804E5C3555E2AD3CCA6FADCB" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentPeriodEndDate" xlink:label="loc_dei_DocumentPeriodEndDate_CA1C6817612113930121AD3CCA702FD9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_DocumentPeriodEndDate_CA1C6817612113930121AD3CCA702FD9" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentFiscalYearFocus" xlink:label="loc_dei_DocumentFiscalYearFocus_0C528AA8BF448CA087E6AD3CCA7068CF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_DocumentFiscalYearFocus_0C528AA8BF448CA087E6AD3CCA7068CF" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="loc_dei_DocumentFiscalPeriodFocus_FC54D7B8C338E8454A0EAD3CCA7085A8" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_DocumentFiscalPeriodFocus_FC54D7B8C338E8454A0EAD3CCA7085A8" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_TradingSymbol" xlink:label="loc_dei_TradingSymbol_0E27E28372D77F9529CFAD3CCA70B7DC" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_TradingSymbol_0E27E28372D77F9529CFAD3CCA70B7DC" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityRegistrantName" xlink:label="loc_dei_EntityRegistrantName_845323F5C1E0608EBAEEAD3CCA704874" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_EntityRegistrantName_845323F5C1E0608EBAEEAD3CCA704874" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityCentralIndexKey" xlink:label="loc_dei_EntityCentralIndexKey_E71E754985B6F60133A8AD3CCA7008C3" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_EntityCentralIndexKey_E71E754985B6F60133A8AD3CCA7008C3" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_CurrentFiscalYearEndDate" xlink:label="loc_dei_CurrentFiscalYearEndDate_667EB7DEA911753705A3AD3CCA71CFD4" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_CurrentFiscalYearEndDate_667EB7DEA911753705A3AD3CCA71CFD4" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityFilerCategory" xlink:label="loc_dei_EntityFilerCategory_CC1C9A4A21A251B3AF54AD3CCA71FE9D" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_EntityFilerCategory_CC1C9A4A21A251B3AF54AD3CCA71FE9D" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntitySmallBusiness" xlink:label="loc_dei_EntitySmallBusiness_DA234AE179B133EB12EDAD5B9B4E0B22" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_EntitySmallBusiness_DA234AE179B133EB12EDAD5B9B4E0B22" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityEmergingGrowthCompany" xlink:label="loc_dei_EntityEmergingGrowthCompany_129E6DEAEE7D04C4F7E0AD5D6C3CC060" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_EntityEmergingGrowthCompany_129E6DEAEE7D04C4F7E0AD5D6C3CC060" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_E6C38AD31A5D064DB433AD3CCA717BC6" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_B92C43407DADE1611429AD3CCA6FC353" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_E6C38AD31A5D064DB433AD3CCA717BC6" 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/FairValueMeasurementsSummaryOfCarryingAndFairValuesOfLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_620FF911DEC2B10695657EB341C253E6" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_E0CE848D95AD3C3CB4207EB341C25632" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_620FF911DEC2B10695657EB341C253E6" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_E0CE848D95AD3C3CB4207EB341C25632" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_88E38C16AE09E17B23B97EB341C2083C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_E0CE848D95AD3C3CB4207EB341C25632" xlink:to="loc_us-gaap_DebtInstrumentAxis_88E38C16AE09E17B23B97EB341C2083C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_3BA4490607AB1AEEF12A7EB341C2AFE8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_88E38C16AE09E17B23B97EB341C2083C" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3BA4490607AB1AEEF12A7EB341C2AFE8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_3BA4490607AB1AEEF12A7EB341C2AFE8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_88E38C16AE09E17B23B97EB341C2083C" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3BA4490607AB1AEEF12A7EB341C2AFE8" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_OpCoRevolverMember" xlink:label="loc_wlkp_OpCoRevolverMember_26652CD47179476AE3567EB341C21377" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3BA4490607AB1AEEF12A7EB341C2AFE8" xlink:to="loc_wlkp_OpCoRevolverMember_26652CD47179476AE3567EB341C21377" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_MLPRevolverMember" xlink:label="loc_wlkp_MLPRevolverMember_4EDFDE52C275650051937EB341C2A884" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3BA4490607AB1AEEF12A7EB341C2AFE8" xlink:to="loc_wlkp_MLPRevolverMember_4EDFDE52C275650051937EB341C2A884" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_72E87A7E7C6F7F230A8F7EB341C27736" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_E0CE848D95AD3C3CB4207EB341C25632" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_72E87A7E7C6F7F230A8F7EB341C27736" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_F235368E430EBF4830477EB341C2D33D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_72E87A7E7C6F7F230A8F7EB341C27736" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_F235368E430EBF4830477EB341C2D33D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_F235368E430EBF4830477EB341C2D33D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_72E87A7E7C6F7F230A8F7EB341C27736" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_F235368E430EBF4830477EB341C2D33D" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SeniorUnsecuredRevolvingCreditFacilityMember" xlink:label="loc_wlkp_SeniorUnsecuredRevolvingCreditFacilityMember_17C94676F55C506C61CF7EB341C20315" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_F235368E430EBF4830477EB341C2D33D" xlink:to="loc_wlkp_SeniorUnsecuredRevolvingCreditFacilityMember_17C94676F55C506C61CF7EB341C20315" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_056534080AA3E85093677EB341C2AE13" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_E0CE848D95AD3C3CB4207EB341C25632" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_056534080AA3E85093677EB341C2AE13" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_3837854A648032F1426F7EB341C2BA4F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_056534080AA3E85093677EB341C2AE13" xlink:to="loc_us-gaap_RelatedPartyDomain_3837854A648032F1426F7EB341C2BA4F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_3837854A648032F1426F7EB341C2BA4F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_056534080AA3E85093677EB341C2AE13" xlink:to="loc_us-gaap_RelatedPartyDomain_3837854A648032F1426F7EB341C2BA4F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_14E795F10C944E145B2D7EB341C237E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_3837854A648032F1426F7EB341C2BA4F" xlink:to="loc_us-gaap_LimitedPartnerMember_14E795F10C944E145B2D7EB341C237E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DueToRelatedPartiesNoncurrent" xlink:label="loc_us-gaap_DueToRelatedPartiesNoncurrent_2A26E82D0ADF05AF345A7EB341C29505" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_620FF911DEC2B10695657EB341C253E6" xlink:to="loc_us-gaap_DueToRelatedPartiesNoncurrent_2A26E82D0ADF05AF345A7EB341C29505" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtFairValue" xlink:label="loc_us-gaap_LongTermDebtFairValue_8E386AE32E714CBD8E587EB341C22C85" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_620FF911DEC2B10695657EB341C253E6" xlink:to="loc_us-gaap_LongTermDebtFairValue_8E386AE32E714CBD8E587EB341C22C85" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_A83579F53868DEAD6DF07EB1B9D5BC3E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_1C913E7C2862C288A0C47EB1B9D565A7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_A83579F53868DEAD6DF07EB1B9D5BC3E" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_1C913E7C2862C288A0C47EB1B9D565A7" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_C57E274543CCC12260697EB1B9D554C7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_1C913E7C2862C288A0C47EB1B9D565A7" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_C57E274543CCC12260697EB1B9D554C7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_AD62B3F42125F21921747EB1B9D59BEE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_C57E274543CCC12260697EB1B9D554C7" xlink:to="loc_us-gaap_RelatedPartyDomain_AD62B3F42125F21921747EB1B9D59BEE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_AD62B3F42125F21921747EB1B9D59BEE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_C57E274543CCC12260697EB1B9D554C7" xlink:to="loc_us-gaap_RelatedPartyDomain_AD62B3F42125F21921747EB1B9D59BEE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_0E996F9DB62A4643523B7EB1B9D51AEF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_AD62B3F42125F21921747EB1B9D59BEE" xlink:to="loc_us-gaap_LimitedPartnerMember_0E996F9DB62A4643523B7EB1B9D51AEF" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_69AFEC1F4A2ABD6991697EB1B9D563D3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_1C913E7C2862C288A0C47EB1B9D565A7" xlink:to="loc_dei_LegalEntityAxis_69AFEC1F4A2ABD6991697EB1B9D563D3" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_2BE368758E2A080AB2DB7EB1B9D55CC6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_69AFEC1F4A2ABD6991697EB1B9D563D3" xlink:to="loc_dei_EntityDomain_2BE368758E2A080AB2DB7EB1B9D55CC6_default" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_2BE368758E2A080AB2DB7EB1B9D55CC6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_69AFEC1F4A2ABD6991697EB1B9D563D3" xlink:to="loc_dei_EntityDomain_2BE368758E2A080AB2DB7EB1B9D55CC6" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_OpCoRevolverMember" xlink:label="loc_wlkp_OpCoRevolverMember_EA10827E1C83BE62565E7EB1B9D51876" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_2BE368758E2A080AB2DB7EB1B9D55CC6" xlink:to="loc_wlkp_OpCoRevolverMember_EA10827E1C83BE62565E7EB1B9D51876" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_D7D1BD3C44B8AAC949157EB1B9D50EDE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_1C913E7C2862C288A0C47EB1B9D565A7" xlink:to="loc_us-gaap_DebtInstrumentAxis_D7D1BD3C44B8AAC949157EB1B9D50EDE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_08640B09356AB16E3FA27EB1B9D5014E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_D7D1BD3C44B8AAC949157EB1B9D50EDE" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_08640B09356AB16E3FA27EB1B9D5014E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_08640B09356AB16E3FA27EB1B9D5014E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_D7D1BD3C44B8AAC949157EB1B9D50EDE" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_08640B09356AB16E3FA27EB1B9D5014E" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_OpCoRevolverMember" xlink:label="loc_wlkp_OpCoRevolverMember_342780A5BD40961912017EB1B9D589D4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_08640B09356AB16E3FA27EB1B9D5014E" xlink:to="loc_wlkp_OpCoRevolverMember_342780A5BD40961912017EB1B9D589D4" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_MLPRevolverMember" xlink:label="loc_wlkp_MLPRevolverMember_F692AECD911413551E907EB1B9D53F97" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_08640B09356AB16E3FA27EB1B9D5014E" xlink:to="loc_wlkp_MLPRevolverMember_F692AECD911413551E907EB1B9D53F97" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_F0B52680278CDAD4B2EF7EB1B9D59057" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_1C913E7C2862C288A0C47EB1B9D565A7" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_F0B52680278CDAD4B2EF7EB1B9D59057" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_570DDCD1C20B72B8D93F7EB1B9D55F4D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_F0B52680278CDAD4B2EF7EB1B9D59057" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_570DDCD1C20B72B8D93F7EB1B9D55F4D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_570DDCD1C20B72B8D93F7EB1B9D55F4D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_F0B52680278CDAD4B2EF7EB1B9D59057" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_570DDCD1C20B72B8D93F7EB1B9D55F4D" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SeniorUnsecuredRevolvingCreditFacilityMember" xlink:label="loc_wlkp_SeniorUnsecuredRevolvingCreditFacilityMember_2A2D7DB6184B7121ABBA7EB1B9D5D59A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_570DDCD1C20B72B8D93F7EB1B9D55F4D" xlink:to="loc_wlkp_SeniorUnsecuredRevolvingCreditFacilityMember_2A2D7DB6184B7121ABBA7EB1B9D5D59A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="loc_us-gaap_VariableRateAxis_E6D7E1C1F1566B839BDC7EB1B9D5B1C5" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_1C913E7C2862C288A0C47EB1B9D565A7" xlink:to="loc_us-gaap_VariableRateAxis_E6D7E1C1F1566B839BDC7EB1B9D5B1C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_12769D38797B29680C0B7EB1B9D574EC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_E6D7E1C1F1566B839BDC7EB1B9D5B1C5" xlink:to="loc_us-gaap_VariableRateDomain_12769D38797B29680C0B7EB1B9D574EC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_12769D38797B29680C0B7EB1B9D574EC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_E6D7E1C1F1566B839BDC7EB1B9D5B1C5" xlink:to="loc_us-gaap_VariableRateDomain_12769D38797B29680C0B7EB1B9D574EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_682CFCDD36C8C752FA737EB1B9D5CA82" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_12769D38797B29680C0B7EB1B9D574EC" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_682CFCDD36C8C752FA737EB1B9D5CA82" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DueToRelatedPartiesNoncurrent" xlink:label="loc_us-gaap_DueToRelatedPartiesNoncurrent_E62E4B42D1477AD208917EB1B9D52715" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_A83579F53868DEAD6DF07EB1B9D5BC3E" xlink:to="loc_us-gaap_DueToRelatedPartiesNoncurrent_E62E4B42D1477AD208917EB1B9D52715" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongtermDebtWeightedAverageInterestRate" xlink:label="loc_us-gaap_LongtermDebtWeightedAverageInterestRate_51D90020FA78848BF32F7EB1B9D5338D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_A83579F53868DEAD6DF07EB1B9D5BC3E" xlink:to="loc_us-gaap_LongtermDebtWeightedAverageInterestRate_51D90020FA78848BF32F7EB1B9D5338D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_279B494CC5F5BFE7953B7EB1B9D5F750" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_A83579F53868DEAD6DF07EB1B9D5BC3E" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_279B494CC5F5BFE7953B7EB1B9D5F750" 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/OtherAssets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/OtherAssetsDetails" xlink:type="extended">
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_OtherAssetsLineItems" xlink:label="loc_wlkp_OtherAssetsLineItems_F186652074A4C1F2314B3A0B45578058" xlink:type="locator" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ScheduleOfOtherAssetsTable" xlink:label="loc_wlkp_ScheduleOfOtherAssetsTable_13C0A845CE85C9246E8D3A0B4557B156" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_wlkp_OtherAssetsLineItems_F186652074A4C1F2314B3A0B45578058" xlink:to="loc_wlkp_ScheduleOfOtherAssetsTable_13C0A845CE85C9246E8D3A0B4557B156" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_24AAD7287697ABCB57103A0B455765E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_wlkp_ScheduleOfOtherAssetsTable_13C0A845CE85C9246E8D3A0B4557B156" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_24AAD7287697ABCB57103A0B455765E0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_CECAD6F4FDBE436BA4C53A0B45574327_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_24AAD7287697ABCB57103A0B455765E0" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_CECAD6F4FDBE436BA4C53A0B45574327_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_CECAD6F4FDBE436BA4C53A0B45574327" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_24AAD7287697ABCB57103A0B455765E0" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_CECAD6F4FDBE436BA4C53A0B45574327" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherAssetsMember" xlink:label="loc_us-gaap_OtherAssetsMember_8A697A17CB4A2C6183983A0B455777D9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_CECAD6F4FDBE436BA4C53A0B45574327" xlink:to="loc_us-gaap_OtherAssetsMember_8A697A17CB4A2C6183983A0B455777D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdjustmentForAmortization" xlink:label="loc_us-gaap_AdjustmentForAmortization_6EA3AB1002593BB2E7FC3A0B45574968" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_wlkp_OtherAssetsLineItems_F186652074A4C1F2314B3A0B45578058" xlink:to="loc_us-gaap_AdjustmentForAmortization_6EA3AB1002593BB2E7FC3A0B45574968" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/PartnersEquity" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.westlake.com/role/PartnersEquityDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_A5DE1DEC7BB7087B1A0CAD3CC9636011" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_828B896DD3944CB2A36CAD3CC9609189" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_A5DE1DEC7BB7087B1A0CAD3CC9636011" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_828B896DD3944CB2A36CAD3CC9609189" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_562D770411D157F6FFA6AD3CC9610B8F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_828B896DD3944CB2A36CAD3CC9609189" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_562D770411D157F6FFA6AD3CC9610B8F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6A72DEADC54BD6B6C0E9AD3CC9616220_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_562D770411D157F6FFA6AD3CC9610B8F" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6A72DEADC54BD6B6C0E9AD3CC9616220_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6A72DEADC54BD6B6C0E9AD3CC9616220" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_562D770411D157F6FFA6AD3CC9610B8F" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6A72DEADC54BD6B6C0E9AD3CC9616220" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnerMember" xlink:label="loc_us-gaap_LimitedPartnerMember_0C91E8EFD1EFA27F1758AD3CC9618B96" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6A72DEADC54BD6B6C0E9AD3CC9616220" xlink:to="loc_us-gaap_LimitedPartnerMember_0C91E8EFD1EFA27F1758AD3CC9618B96" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_176DB1846BB4EDA45070AD3CC962D3D5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_828B896DD3944CB2A36CAD3CC9609189" xlink:to="loc_srt_CounterpartyNameAxis_176DB1846BB4EDA45070AD3CC962D3D5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_19A5729402620845A565AD3CC962C039_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_176DB1846BB4EDA45070AD3CC962D3D5" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_19A5729402620845A565AD3CC962C039_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_19A5729402620845A565AD3CC962C039" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_176DB1846BB4EDA45070AD3CC962D3D5" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_19A5729402620845A565AD3CC962C039" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_F020308D49E5D53F466CAD3CC962CDCA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_19A5729402620845A565AD3CC962C039" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_F020308D49E5D53F466CAD3CC962CDCA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_D2FBE6772A1DADF1AC04AD3CC9624FAD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_828B896DD3944CB2A36CAD3CC9609189" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_D2FBE6772A1DADF1AC04AD3CC9624FAD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_99AAE5BAC0023723E1BBAD3CC962DDCF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_D2FBE6772A1DADF1AC04AD3CC9624FAD" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_99AAE5BAC0023723E1BBAD3CC962DDCF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_99AAE5BAC0023723E1BBAD3CC962DDCF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_D2FBE6772A1DADF1AC04AD3CC9624FAD" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_99AAE5BAC0023723E1BBAD3CC962DDCF" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SubordinatedUnitsMember" xlink:label="loc_wlkp_SubordinatedUnitsMember_CAFAF03329E7B9CCDF68AD3CC9639F63" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_99AAE5BAC0023723E1BBAD3CC962DDCF" xlink:to="loc_wlkp_SubordinatedUnitsMember_CAFAF03329E7B9CCDF68AD3CC9639F63" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_860B70EA68283D0C5A1EAD3CC96383B4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_A5DE1DEC7BB7087B1A0CAD3CC9636011" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_860B70EA68283D0C5A1EAD3CC96383B4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering" xlink:label="loc_us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering_C01DF5DB83C269A2F801AD3CC964AAF3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_A5DE1DEC7BB7087B1A0CAD3CC9636011" xlink:to="loc_us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering_C01DF5DB83C269A2F801AD3CC964AAF3" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit" xlink:label="loc_wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit_220C66CD15D3EE5BB054AD3CC9645A69" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_A5DE1DEC7BB7087B1A0CAD3CC9636011" xlink:to="loc_wlkp_PartnersCapitalAccountUnitsSoldinPublicOfferingPriceperUnit_220C66CD15D3EE5BB054AD3CC9645A69" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity" xlink:label="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_1A725A62ED5FA3419F68AD3CC96443C7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_A5DE1DEC7BB7087B1A0CAD3CC9636011" xlink:to="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_1A725A62ED5FA3419F68AD3CC96443C7" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity" xlink:label="loc_wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity_009D12CC2B75EA8E71D1AD3CC964F310" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_A5DE1DEC7BB7087B1A0CAD3CC9636011" xlink:to="loc_wlkp_UnderwritingDiscountsStructuringFeesandOfferingExpensesonIssuanceofEquity_009D12CC2B75EA8E71D1AD3CC964F310" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_7C670A564B71563F48A23A0B453811AB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_03F4E7B24B435C1234A63A0B45387A94" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7C670A564B71563F48A23A0B453811AB" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_03F4E7B24B435C1234A63A0B45387A94" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_02269140CBD43C819F9C3A0B4538F14A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_03F4E7B24B435C1234A63A0B45387A94" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_02269140CBD43C819F9C3A0B4538F14A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_CDB687AB3E86E362F72A3A0B45385C19_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_02269140CBD43C819F9C3A0B4538F14A" xlink:to="loc_us-gaap_RelatedPartyDomain_CDB687AB3E86E362F72A3A0B45385C19_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_CDB687AB3E86E362F72A3A0B45385C19" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_02269140CBD43C819F9C3A0B4538F14A" xlink:to="loc_us-gaap_RelatedPartyDomain_CDB687AB3E86E362F72A3A0B45385C19" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_AffiliatedEntityMember" xlink:label="loc_srt_AffiliatedEntityMember_C0E7BAF48B5FED9C303F3A0B453822EB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_CDB687AB3E86E362F72A3A0B45385C19" xlink:to="loc_srt_AffiliatedEntityMember_C0E7BAF48B5FED9C303F3A0B453822EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_B19F6558A7B9C650DBF53A0B4538351B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_03F4E7B24B435C1234A63A0B45387A94" xlink:to="loc_srt_CounterpartyNameAxis_B19F6558A7B9C650DBF53A0B4538351B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_CB410F8F7BA2321C4AFD3A0B4538DB21_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_B19F6558A7B9C650DBF53A0B4538351B" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_CB410F8F7BA2321C4AFD3A0B4538DB21_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_CB410F8F7BA2321C4AFD3A0B4538DB21" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_B19F6558A7B9C650DBF53A0B4538351B" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_CB410F8F7BA2321C4AFD3A0B4538DB21" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_345C54567D45E54C62D83A0B453801E7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_CB410F8F7BA2321C4AFD3A0B4538DB21" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_345C54567D45E54C62D83A0B453801E7" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent" xlink:label="loc_wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent_8E9E601A18C1BE8DCE5A3A0B4538969F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7C670A564B71563F48A23A0B453811AB" xlink:to="loc_wlkp_ReceivablesunderInvestmentManagementAgreementswithRelatedPartiesCurrent_8E9E601A18C1BE8DCE5A3A0B4538969F" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_AccountsReceivableRelatedpartiesCurrentandNoncurrent" xlink:label="loc_wlkp_AccountsReceivableRelatedpartiesCurrentandNoncurrent_835DB4F8AF194230BF613A0B4538FB98" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7C670A564B71563F48A23A0B453811AB" xlink:to="loc_wlkp_AccountsReceivableRelatedpartiesCurrentandNoncurrent_835DB4F8AF194230BF613A0B4538FB98" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsPayableRelatedPartiesCurrent" xlink:label="loc_us-gaap_AccountsPayableRelatedPartiesCurrent_FA76CB952C40CA5A5D0D3A0B45384582" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_7C670A564B71563F48A23A0B453811AB" xlink:to="loc_us-gaap_AccountsPayableRelatedPartiesCurrent_FA76CB952C40CA5A5D0D3A0B45384582" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_C7C19DF22A1801843E213A0B45861B75" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_134DF913A1614FFEA9653A0B45765450" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_C7C19DF22A1801843E213A0B45861B75" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_134DF913A1614FFEA9653A0B45765450" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_131BAB7577685DD4365F3A0B4576EED0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_134DF913A1614FFEA9653A0B45765450" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_131BAB7577685DD4365F3A0B4576EED0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_D7100B613D3A4E2C46C43A0B45761E24_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_131BAB7577685DD4365F3A0B4576EED0" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_D7100B613D3A4E2C46C43A0B45761E24_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_D7100B613D3A4E2C46C43A0B45761E24" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_131BAB7577685DD4365F3A0B4576EED0" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_D7100B613D3A4E2C46C43A0B45761E24" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_FeedstockPurchasedMember" xlink:label="loc_wlkp_FeedstockPurchasedMember_99E995649B14BB50BD193A0B4576914D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_D7100B613D3A4E2C46C43A0B45761E24" xlink:to="loc_wlkp_FeedstockPurchasedMember_99E995649B14BB50BD193A0B4576914D" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_OtherServiceChargesMember" xlink:label="loc_wlkp_OtherServiceChargesMember_B46A1C1C357BA628186A3A0B45763BE4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_D7100B613D3A4E2C46C43A0B45761E24" xlink:to="loc_wlkp_OtherServiceChargesMember_B46A1C1C357BA628186A3A0B45763BE4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B346589529E6B9CA33A53A0B4586C7BB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_134DF913A1614FFEA9653A0B45765450" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B346589529E6B9CA33A53A0B4586C7BB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_23EB1DE3F02A1896BA513A0B45860222_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B346589529E6B9CA33A53A0B4586C7BB" xlink:to="loc_us-gaap_RelatedPartyDomain_23EB1DE3F02A1896BA513A0B45860222_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_23EB1DE3F02A1896BA513A0B45860222" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B346589529E6B9CA33A53A0B4586C7BB" xlink:to="loc_us-gaap_RelatedPartyDomain_23EB1DE3F02A1896BA513A0B45860222" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_AffiliatedEntityMember" xlink:label="loc_srt_AffiliatedEntityMember_4720BC0055FF780004B23A0B4586829E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_23EB1DE3F02A1896BA513A0B45860222" xlink:to="loc_srt_AffiliatedEntityMember_4720BC0055FF780004B23A0B4586829E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_46DEC34EC7705F092C503A0B4586C80A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_134DF913A1614FFEA9653A0B45765450" xlink:to="loc_srt_CounterpartyNameAxis_46DEC34EC7705F092C503A0B4586C80A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_2B4A9FBCECDE74B10F393A0B45864DE5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_46DEC34EC7705F092C503A0B4586C80A" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_2B4A9FBCECDE74B10F393A0B45864DE5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_2B4A9FBCECDE74B10F393A0B45864DE5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_46DEC34EC7705F092C503A0B4586C80A" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_2B4A9FBCECDE74B10F393A0B45864DE5" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_0478633B5F6723361B983A0B458640FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_2B4A9FBCECDE74B10F393A0B45864DE5" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_0478633B5F6723361B983A0B458640FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartiesAmountInCostOfSales" xlink:label="loc_us-gaap_RelatedPartiesAmountInCostOfSales_9F6ACE05B758E8B9FC193A0B45869C55" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_C7C19DF22A1801843E213A0B45861B75" xlink:to="loc_us-gaap_RelatedPartiesAmountInCostOfSales_9F6ACE05B758E8B9FC193A0B45869C55" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_CAF8A77175FCD69CEC537EAB17D82808" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3161F355DBB41708BBED7EAB17D880C1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_CAF8A77175FCD69CEC537EAB17D82808" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3161F355DBB41708BBED7EAB17D880C1" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_D936445B834992295A6C7EAB17D867CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3161F355DBB41708BBED7EAB17D880C1" xlink:to="loc_dei_LegalEntityAxis_D936445B834992295A6C7EAB17D867CA" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_E6F05E5CFE55870093E97EAB17D8FB67_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_D936445B834992295A6C7EAB17D867CA" xlink:to="loc_dei_EntityDomain_E6F05E5CFE55870093E97EAB17D8FB67_default" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_E6F05E5CFE55870093E97EAB17D8FB67" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_D936445B834992295A6C7EAB17D867CA" xlink:to="loc_dei_EntityDomain_E6F05E5CFE55870093E97EAB17D8FB67" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_1FF955EB52C2239630907EAB17D853DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_E6F05E5CFE55870093E97EAB17D8FB67" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_1FF955EB52C2239630907EAB17D853DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis" xlink:label="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_5E9AD6C5243AB887E1F87EAB17D8A013" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3161F355DBB41708BBED7EAB17D880C1" xlink:to="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_5E9AD6C5243AB887E1F87EAB17D8A013" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_5CDD5FACB0270E0594B27EAB17D8D41E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_5E9AD6C5243AB887E1F87EAB17D8A013" xlink:to="loc_us-gaap_DistributionTypeDomain_5CDD5FACB0270E0594B27EAB17D8D41E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_5CDD5FACB0270E0594B27EAB17D8D41E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_5E9AD6C5243AB887E1F87EAB17D8A013" xlink:to="loc_us-gaap_DistributionTypeDomain_5CDD5FACB0270E0594B27EAB17D8D41E" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CashDistributionTrancheOneMember" xlink:label="loc_wlkp_CashDistributionTrancheOneMember_EC806B1E17DC3BCADB077EAB17D8F0A5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionTypeDomain_5CDD5FACB0270E0594B27EAB17D8D41E" xlink:to="loc_wlkp_CashDistributionTrancheOneMember_EC806B1E17DC3BCADB077EAB17D8F0A5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_E60DD0E5F824D155A97F7EAB17D87A1F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3161F355DBB41708BBED7EAB17D880C1" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_E60DD0E5F824D155A97F7EAB17D87A1F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_7BEBCE2ADFA1E831FD5F7EAB17D80999_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_E60DD0E5F824D155A97F7EAB17D87A1F" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_7BEBCE2ADFA1E831FD5F7EAB17D80999_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_7BEBCE2ADFA1E831FD5F7EAB17D80999" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_E60DD0E5F824D155A97F7EAB17D87A1F" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_7BEBCE2ADFA1E831FD5F7EAB17D80999" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_D2DC8661FB0EC3D9787C7EAB17D8EEA8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_7BEBCE2ADFA1E831FD5F7EAB17D80999" xlink:to="loc_wlkp_IDRHoldersMember_D2DC8661FB0EC3D9787C7EAB17D8EEA8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_12F8AFD32B34871005A37EAB17D8FB72" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3161F355DBB41708BBED7EAB17D880C1" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_12F8AFD32B34871005A37EAB17D8FB72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_D02D8FC295BC103C4D8A7EAB17D88824_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_12F8AFD32B34871005A37EAB17D8FB72" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_D02D8FC295BC103C4D8A7EAB17D88824_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_D02D8FC295BC103C4D8A7EAB17D88824" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_12F8AFD32B34871005A37EAB17D8FB72" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_D02D8FC295BC103C4D8A7EAB17D88824" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccruedLiabilitiesMember" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_74D383A6758641B129E77EAB17D85CDF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_D02D8FC295BC103C4D8A7EAB17D88824" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_74D383A6758641B129E77EAB17D85CDF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_4B98E7A7223BE20EA4B67EAB17D86AA2" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3161F355DBB41708BBED7EAB17D880C1" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_4B98E7A7223BE20EA4B67EAB17D86AA2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_437371C6968F21B31AC17EAB17D809B3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_4B98E7A7223BE20EA4B67EAB17D86AA2" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_437371C6968F21B31AC17EAB17D809B3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_437371C6968F21B31AC17EAB17D809B3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_4B98E7A7223BE20EA4B67EAB17D86AA2" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_437371C6968F21B31AC17EAB17D809B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpenseMember" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpenseMember_C04F26E7210B834FBB9A7EAB17D8CD77" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_437371C6968F21B31AC17EAB17D809B3" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpenseMember_C04F26E7210B834FBB9A7EAB17D8CD77" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_CB3D6407419EB291C5407EAB17D8ECD3" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3161F355DBB41708BBED7EAB17D880C1" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_CB3D6407419EB291C5407EAB17D8ECD3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_ABE71C2E32F06A9137ED7EAB17D8E782_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_CB3D6407419EB291C5407EAB17D8ECD3" xlink:to="loc_us-gaap_RelatedPartyDomain_ABE71C2E32F06A9137ED7EAB17D8E782_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_ABE71C2E32F06A9137ED7EAB17D8E782" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_CB3D6407419EB291C5407EAB17D8ECD3" xlink:to="loc_us-gaap_RelatedPartyDomain_ABE71C2E32F06A9137ED7EAB17D8E782" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_AffiliatedEntityMember" xlink:label="loc_srt_AffiliatedEntityMember_4A264D1945BB3C422E317EAB17D8A930" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_ABE71C2E32F06A9137ED7EAB17D8E782" xlink:to="loc_srt_AffiliatedEntityMember_4A264D1945BB3C422E317EAB17D8A930" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_A25EF302F92A5144BEAE7EAB17D8A687" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3161F355DBB41708BBED7EAB17D880C1" xlink:to="loc_srt_CounterpartyNameAxis_A25EF302F92A5144BEAE7EAB17D8A687" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_3255CBADFF6088CDA30C7EAB17D8D7CB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_A25EF302F92A5144BEAE7EAB17D8A687" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_3255CBADFF6088CDA30C7EAB17D8D7CB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_3255CBADFF6088CDA30C7EAB17D8D7CB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_A25EF302F92A5144BEAE7EAB17D8A687" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_3255CBADFF6088CDA30C7EAB17D8D7CB" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_049A2EBD863A77F3B9307EAB17D8FD7E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_3255CBADFF6088CDA30C7EAB17D8D7CB" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_049A2EBD863A77F3B9307EAB17D8FD7E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestExpenseRelatedParty" xlink:label="loc_us-gaap_InterestExpenseRelatedParty_532C268E38016005B24C7EAB17D88C12" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_CAF8A77175FCD69CEC537EAB17D82808" xlink:to="loc_us-gaap_InterestExpenseRelatedParty_532C268E38016005B24C7EAB17D88C12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestCostsCapitalized" xlink:label="loc_us-gaap_InterestCostsCapitalized_6D051A4E1E8BABEBC8DA7EAB17D878ED" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_CAF8A77175FCD69CEC537EAB17D82808" xlink:to="loc_us-gaap_InterestCostsCapitalized_6D051A4E1E8BABEBC8DA7EAB17D878ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestPayableCurrent" xlink:label="loc_us-gaap_InterestPayableCurrent_5E36F99BB888A205BE917EAB17D86858" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_CAF8A77175FCD69CEC537EAB17D82808" xlink:to="loc_us-gaap_InterestPayableCurrent_5E36F99BB888A205BE917EAB17D86858" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DueToRelatedPartiesNoncurrent" xlink:label="loc_us-gaap_DueToRelatedPartiesNoncurrent_3BBE566616FBA998EFE57EAB17D860C9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_CAF8A77175FCD69CEC537EAB17D82808" xlink:to="loc_us-gaap_DueToRelatedPartiesNoncurrent_3BBE566616FBA998EFE57EAB17D860C9" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_15FC83350B83AD1B55867ED6DED4097D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_D9E19599C2A7A001D4937ED6DED4F6E1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_15FC83350B83AD1B55867ED6DED4097D" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_D9E19599C2A7A001D4937ED6DED4F6E1" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_65299EE4F8DD6A7FC06A7ED6DED40BFA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_D9E19599C2A7A001D4937ED6DED4F6E1" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_65299EE4F8DD6A7FC06A7ED6DED40BFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_628DE74D87EA4BE24A717ED6DED4BBBA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_65299EE4F8DD6A7FC06A7ED6DED40BFA" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_628DE74D87EA4BE24A717ED6DED4BBBA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_628DE74D87EA4BE24A717ED6DED4BBBA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_65299EE4F8DD6A7FC06A7ED6DED40BFA" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_628DE74D87EA4BE24A717ED6DED4BBBA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccruedLiabilitiesMember" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_FD52F5F2C92D1D6851B07ED6DED429D0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_628DE74D87EA4BE24A717ED6DED4BBBA" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_FD52F5F2C92D1D6851B07ED6DED429D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis" xlink:label="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_3AEDCD992A6B6F07FFE17ED6DED4E7B3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_D9E19599C2A7A001D4937ED6DED4F6E1" xlink:to="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_3AEDCD992A6B6F07FFE17ED6DED4E7B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_EC16EBD06394CBBDC14E7ED6DED438C0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_3AEDCD992A6B6F07FFE17ED6DED4E7B3" xlink:to="loc_us-gaap_DistributionTypeDomain_EC16EBD06394CBBDC14E7ED6DED438C0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DistributionTypeDomain" xlink:label="loc_us-gaap_DistributionTypeDomain_EC16EBD06394CBBDC14E7ED6DED438C0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DistributionsMadeToMemberOrLimitedPartnerByDistributionTypeAxis_3AEDCD992A6B6F07FFE17ED6DED4E7B3" xlink:to="loc_us-gaap_DistributionTypeDomain_EC16EBD06394CBBDC14E7ED6DED438C0" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_CashDistributionTrancheOneMember" xlink:label="loc_wlkp_CashDistributionTrancheOneMember_37289B9CD52FD18F282D7ED6DED4FC92" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DistributionTypeDomain_EC16EBD06394CBBDC14E7ED6DED438C0" xlink:to="loc_wlkp_CashDistributionTrancheOneMember_37289B9CD52FD18F282D7ED6DED4FC92" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis" xlink:label="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_69158037DBAC89C2F6EF7ED6DED4F347" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_D9E19599C2A7A001D4937ED6DED4F6E1" xlink:to="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_69158037DBAC89C2F6EF7ED6DED4F347" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_0116531C72B6F15188F57ED6DED4B4A4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_69158037DBAC89C2F6EF7ED6DED4F347" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_0116531C72B6F15188F57ED6DED4B4A4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncentiveDistributionRecipientDomain" xlink:label="loc_us-gaap_IncentiveDistributionRecipientDomain_0116531C72B6F15188F57ED6DED4B4A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncentiveDistributionMadeToManagingMemberOrGeneralPartnerAxis_69158037DBAC89C2F6EF7ED6DED4F347" xlink:to="loc_us-gaap_IncentiveDistributionRecipientDomain_0116531C72B6F15188F57ED6DED4B4A4" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_IDRHoldersMember" xlink:label="loc_wlkp_IDRHoldersMember_D1F85F3422465E70BC137ED6DED4BDDE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncentiveDistributionRecipientDomain_0116531C72B6F15188F57ED6DED4B4A4" xlink:to="loc_wlkp_IDRHoldersMember_D1F85F3422465E70BC137ED6DED4BDDE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_AE3A2FB906420BCDDEB27ED6DED43F0A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_D9E19599C2A7A001D4937ED6DED4F6E1" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_AE3A2FB906420BCDDEB27ED6DED43F0A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_AFA024BED1B2B54F49A47ED6DED43D71_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_AE3A2FB906420BCDDEB27ED6DED43F0A" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_AFA024BED1B2B54F49A47ED6DED43D71_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_AFA024BED1B2B54F49A47ED6DED43D71" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_AE3A2FB906420BCDDEB27ED6DED43F0A" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_AFA024BED1B2B54F49A47ED6DED43D71" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SiteLeaseAgreementMember" xlink:label="loc_wlkp_SiteLeaseAgreementMember_06BBB9B49214C329BC027ED6DED431CE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_AFA024BED1B2B54F49A47ED6DED43D71" xlink:to="loc_wlkp_SiteLeaseAgreementMember_06BBB9B49214C329BC027ED6DED431CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_BB06C3EBED2F4BB739A77ED6DED497CB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_D9E19599C2A7A001D4937ED6DED4F6E1" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_BB06C3EBED2F4BB739A77ED6DED497CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_EABFB37E0FEB5348418B7ED6DED41E0A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_BB06C3EBED2F4BB739A77ED6DED497CB" xlink:to="loc_us-gaap_RelatedPartyDomain_EABFB37E0FEB5348418B7ED6DED41E0A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_EABFB37E0FEB5348418B7ED6DED41E0A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_BB06C3EBED2F4BB739A77ED6DED497CB" xlink:to="loc_us-gaap_RelatedPartyDomain_EABFB37E0FEB5348418B7ED6DED41E0A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_AffiliatedEntityMember" xlink:label="loc_srt_AffiliatedEntityMember_B5CCD057B3592D19092D7ED6DED482C6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_EABFB37E0FEB5348418B7ED6DED41E0A" xlink:to="loc_srt_AffiliatedEntityMember_B5CCD057B3592D19092D7ED6DED482C6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_52F8E45F6A9992D31A627ED6DED46369" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_D9E19599C2A7A001D4937ED6DED4F6E1" xlink:to="loc_srt_CounterpartyNameAxis_52F8E45F6A9992D31A627ED6DED46369" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_936B3CDE2B8B1BE7FC567ED6DED4A00C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_52F8E45F6A9992D31A627ED6DED46369" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_936B3CDE2B8B1BE7FC567ED6DED4A00C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_936B3CDE2B8B1BE7FC567ED6DED4A00C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_52F8E45F6A9992D31A627ED6DED46369" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_936B3CDE2B8B1BE7FC567ED6DED4A00C" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_DC8325C67FC6D7E8ADD07ED6DED48323" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_936B3CDE2B8B1BE7FC567ED6DED4A00C" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_DC8325C67FC6D7E8ADD07ED6DED48323" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_B75A63BA4DBB63C8CCEC7ED6DED4F5D3" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_D9E19599C2A7A001D4937ED6DED4F6E1" xlink:to="loc_dei_LegalEntityAxis_B75A63BA4DBB63C8CCEC7ED6DED4F5D3" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_91F060EE89CD80A6F6DC7ED6DED40CD2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_B75A63BA4DBB63C8CCEC7ED6DED4F5D3" xlink:to="loc_dei_EntityDomain_91F060EE89CD80A6F6DC7ED6DED40CD2_default" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_91F060EE89CD80A6F6DC7ED6DED40CD2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_B75A63BA4DBB63C8CCEC7ED6DED4F5D3" xlink:to="loc_dei_EntityDomain_91F060EE89CD80A6F6DC7ED6DED40CD2" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_WestlakeChemicalOpCoLPMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoLPMember_954E52F8D792539FEF5B7ED6DED45232" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_91F060EE89CD80A6F6DC7ED6DED40CD2" xlink:to="loc_wlkp_WestlakeChemicalOpCoLPMember_954E52F8D792539FEF5B7ED6DED45232" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_2169A480AD0FD29964EB7ED6DED45401" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_91F060EE89CD80A6F6DC7ED6DED40CD2" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_2169A480AD0FD29964EB7ED6DED45401" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_Reimbursedincometaxpayments" xlink:label="loc_wlkp_Reimbursedincometaxpayments_CCBAD95CF021573458437EE316815BA7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_15FC83350B83AD1B55867ED6DED4097D" xlink:to="loc_wlkp_Reimbursedincometaxpayments_CCBAD95CF021573458437EE316815BA7" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_AccruedinterestincludedinreceivableunderIMA" xlink:label="loc_wlkp_AccruedinterestincludedinreceivableunderIMA_852773F729EB513C76B97ED6DED4D350" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_15FC83350B83AD1B55867ED6DED4097D" xlink:to="loc_wlkp_AccruedinterestincludedinreceivableunderIMA_852773F729EB513C76B97ED6DED4D350" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_InterestearnedrelatedtotheIMA" xlink:label="loc_wlkp_InterestearnedrelatedtotheIMA_C3DBC5071B64D2E107F47ED6DED4F126" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_15FC83350B83AD1B55867ED6DED4097D" xlink:to="loc_wlkp_InterestearnedrelatedtotheIMA_C3DBC5071B64D2E107F47ED6DED4F126" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_D30E2D636935CB60013D3A0B45383AA3" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_FD4DFD4FDF94ED85EECE3A0B4538F633" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D30E2D636935CB60013D3A0B45383AA3" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_FD4DFD4FDF94ED85EECE3A0B4538F633" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0E34044024DDD43A2B513A0B4538694E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_FD4DFD4FDF94ED85EECE3A0B4538F633" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0E34044024DDD43A2B513A0B4538694E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_36BDBE006F92984B007C3A0B4538B1A8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0E34044024DDD43A2B513A0B4538694E" xlink:to="loc_us-gaap_RelatedPartyDomain_36BDBE006F92984B007C3A0B4538B1A8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_36BDBE006F92984B007C3A0B4538B1A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0E34044024DDD43A2B513A0B4538694E" xlink:to="loc_us-gaap_RelatedPartyDomain_36BDBE006F92984B007C3A0B4538B1A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_AffiliatedEntityMember" xlink:label="loc_srt_AffiliatedEntityMember_27D8B30698992848DEB23A0B453843AA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_36BDBE006F92984B007C3A0B4538B1A8" xlink:to="loc_srt_AffiliatedEntityMember_27D8B30698992848DEB23A0B453843AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_337524F9A8AEDBB66B153A0B453828E3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_FD4DFD4FDF94ED85EECE3A0B4538F633" xlink:to="loc_srt_CounterpartyNameAxis_337524F9A8AEDBB66B153A0B453828E3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_E7AB4454FFDA0C79009C3A0B45389F7C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_337524F9A8AEDBB66B153A0B453828E3" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_E7AB4454FFDA0C79009C3A0B45389F7C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_E7AB4454FFDA0C79009C3A0B45389F7C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_337524F9A8AEDBB66B153A0B453828E3" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_E7AB4454FFDA0C79009C3A0B45389F7C" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_14A101B0A7659AF2653D3A0B4538AF56" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_E7AB4454FFDA0C79009C3A0B45389F7C" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_14A101B0A7659AF2653D3A0B4538AF56" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_RelatedPartyTransactionPurchasesFromRelatedPartyCapitalizedAsAssets" xlink:label="loc_wlkp_RelatedPartyTransactionPurchasesFromRelatedPartyCapitalizedAsAssets_B099BEDCA67F17F6ADC43A0B4538BAA2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D30E2D636935CB60013D3A0B45383AA3" xlink:to="loc_wlkp_RelatedPartyTransactionPurchasesFromRelatedPartyCapitalizedAsAssets_B099BEDCA67F17F6ADC43A0B4538BAA2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/RelatedPartyTransactionsMajorCustomerAndConcentrationRiskDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskLineItems" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_AFFA4DE8018F8EF3B42D3A0B4538FF56" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskTable" xlink:label="loc_us-gaap_ConcentrationRiskTable_CEE999051C8DCE6F28C03A0B4528AA5E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_AFFA4DE8018F8EF3B42D3A0B4538FF56" xlink:to="loc_us-gaap_ConcentrationRiskTable_CEE999051C8DCE6F28C03A0B4528AA5E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3C76D54E1B36B35FAE283A0B45287DBF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_CEE999051C8DCE6F28C03A0B4528AA5E" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3C76D54E1B36B35FAE283A0B45287DBF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1B61B47B0491BA0C91A03A0B4528D7FC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3C76D54E1B36B35FAE283A0B45287DBF" xlink:to="loc_us-gaap_RelatedPartyDomain_1B61B47B0491BA0C91A03A0B4528D7FC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1B61B47B0491BA0C91A03A0B4528D7FC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3C76D54E1B36B35FAE283A0B45287DBF" xlink:to="loc_us-gaap_RelatedPartyDomain_1B61B47B0491BA0C91A03A0B4528D7FC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_AffiliatedEntityMember" xlink:label="loc_srt_AffiliatedEntityMember_C1565C4650FAF6DCE51C3A0B45385441" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_1B61B47B0491BA0C91A03A0B4528D7FC" xlink:to="loc_srt_AffiliatedEntityMember_C1565C4650FAF6DCE51C3A0B45385441" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_MajorCustomersAxis" xlink:label="loc_srt_MajorCustomersAxis_A02CF2C70F44CD3521243A0B4538BAE9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_CEE999051C8DCE6F28C03A0B4528AA5E" xlink:to="loc_srt_MajorCustomersAxis_A02CF2C70F44CD3521243A0B4538BAE9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_NameOfMajorCustomerDomain" xlink:label="loc_srt_NameOfMajorCustomerDomain_0A7B3845641C202054CE3A0B45387BBD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_A02CF2C70F44CD3521243A0B4538BAE9" xlink:to="loc_srt_NameOfMajorCustomerDomain_0A7B3845641C202054CE3A0B45387BBD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_NameOfMajorCustomerDomain" xlink:label="loc_srt_NameOfMajorCustomerDomain_0A7B3845641C202054CE3A0B45387BBD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_A02CF2C70F44CD3521243A0B4538BAE9" xlink:to="loc_srt_NameOfMajorCustomerDomain_0A7B3845641C202054CE3A0B45387BBD" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_37DD88F3DF04B3BA68463A0B4538C712" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_0A7B3845641C202054CE3A0B45387BBD" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_37DD88F3DF04B3BA68463A0B4538C712" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_476DC22CF3F8082FFC913A0B4538C357" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_CEE999051C8DCE6F28C03A0B4528AA5E" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_476DC22CF3F8082FFC913A0B4538C357" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_AA24168BBF29591E6E703A0B4538B626_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_476DC22CF3F8082FFC913A0B4538C357" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_AA24168BBF29591E6E703A0B4538B626_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_AA24168BBF29591E6E703A0B4538B626" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_476DC22CF3F8082FFC913A0B4538C357" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_AA24168BBF29591E6E703A0B4538B626" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SalesRevenueNetMember" xlink:label="loc_us-gaap_SalesRevenueNetMember_160415F56526E60D2BAC3A0B4538D6D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_AA24168BBF29591E6E703A0B4538B626" xlink:to="loc_us-gaap_SalesRevenueNetMember_160415F56526E60D2BAC3A0B4538D6D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_DB25086429EF993E57473A0B4538B421" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_CEE999051C8DCE6F28C03A0B4528AA5E" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_DB25086429EF993E57473A0B4538B421" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_CBE95E4B0CCC36F303EE3A0B4538FA11_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_DB25086429EF993E57473A0B4538B421" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_CBE95E4B0CCC36F303EE3A0B4538FA11_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_CBE95E4B0CCC36F303EE3A0B4538FA11" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_DB25086429EF993E57473A0B4538B421" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_CBE95E4B0CCC36F303EE3A0B4538FA11" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_C684898F5A5C8FC160103A0B453858E4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_CBE95E4B0CCC36F303EE3A0B4538FA11" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_C684898F5A5C8FC160103A0B453858E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_53F81DFA57BAD92E83063A0B45385C2B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_AFFA4DE8018F8EF3B42D3A0B4538FF56" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_53F81DFA57BAD92E83063A0B45385C2B" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_22692C3C77A34596644B3A0B46AF8FDA" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_32C59AF277280E5964413A0B46AF1E27" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_22692C3C77A34596644B3A0B46AF8FDA" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_32C59AF277280E5964413A0B46AF1E27" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B7567DDE6EBCE2770B583A0B46AF047E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_32C59AF277280E5964413A0B46AF1E27" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B7567DDE6EBCE2770B583A0B46AF047E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_4C3C22CF601EDEF669F23A0B46AF51C3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B7567DDE6EBCE2770B583A0B46AF047E" xlink:to="loc_us-gaap_RelatedPartyDomain_4C3C22CF601EDEF669F23A0B46AF51C3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_4C3C22CF601EDEF669F23A0B46AF51C3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B7567DDE6EBCE2770B583A0B46AF047E" xlink:to="loc_us-gaap_RelatedPartyDomain_4C3C22CF601EDEF669F23A0B46AF51C3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_AffiliatedEntityMember" xlink:label="loc_srt_AffiliatedEntityMember_FC120F9A3ADEAA01ECBB3A0B46AF42AD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_4C3C22CF601EDEF669F23A0B46AF51C3" xlink:to="loc_srt_AffiliatedEntityMember_FC120F9A3ADEAA01ECBB3A0B46AF42AD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_2B580C9B3BC40088D6663A0B46AF81C9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_32C59AF277280E5964413A0B46AF1E27" xlink:to="loc_srt_CounterpartyNameAxis_2B580C9B3BC40088D6663A0B46AF81C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_33A57B682829CE807AED3A0B46AFE080_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_2B580C9B3BC40088D6663A0B46AF81C9" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_33A57B682829CE807AED3A0B46AFE080_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_33A57B682829CE807AED3A0B46AFE080" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_2B580C9B3BC40088D6663A0B46AF81C9" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_33A57B682829CE807AED3A0B46AFE080" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember" xlink:label="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_8819CF09828437B8F45D3A0B46AF92F3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_33A57B682829CE807AED3A0B46AFE080" xlink:to="loc_wlkp_ParentCompanyAndSubsidiariesExcludingReportingEntityAndSubsidiariesMember_8819CF09828437B8F45D3A0B46AF92F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty" xlink:label="loc_us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty_58BB69490011E5CCC9343A0B46AFCB58" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_22692C3C77A34596644B3A0B46AF8FDA" xlink:to="loc_us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty_58BB69490011E5CCC9343A0B46AFCB58" 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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_6ED127EE4EFCC5C43D233A0B4566037D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C3E3B93EE741591064A63A0B4566DC3A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6ED127EE4EFCC5C43D233A0B4566037D" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C3E3B93EE741591064A63A0B4566DC3A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_DAD932A9FD7D196E60D93A0B456622F9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C3E3B93EE741591064A63A0B4566DC3A" xlink:to="loc_dei_LegalEntityAxis_DAD932A9FD7D196E60D93A0B456622F9" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_DD5F273DDEEFF280937D3A0B45663A67_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_DAD932A9FD7D196E60D93A0B456622F9" xlink:to="loc_dei_EntityDomain_DD5F273DDEEFF280937D3A0B45663A67_default" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_DD5F273DDEEFF280937D3A0B45663A67" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_DAD932A9FD7D196E60D93A0B456622F9" xlink:to="loc_dei_EntityDomain_DD5F273DDEEFF280937D3A0B45663A67" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_WestlakeChemicalOpCoLPMember" xlink:label="loc_wlkp_WestlakeChemicalOpCoLPMember_5EBE4FEAECFAD8C62F283A0B456683F4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_DD5F273DDEEFF280937D3A0B45663A67" xlink:to="loc_wlkp_WestlakeChemicalOpCoLPMember_5EBE4FEAECFAD8C62F283A0B456683F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_62FDB95A03C28BD628143A0B45665802" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C3E3B93EE741591064A63A0B4566DC3A" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_62FDB95A03C28BD628143A0B45665802" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_AE27E1C3F03C3C065DBE3A0B4566245A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_62FDB95A03C28BD628143A0B45665802" xlink:to="loc_us-gaap_RelatedPartyDomain_AE27E1C3F03C3C065DBE3A0B4566245A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_AE27E1C3F03C3C065DBE3A0B4566245A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_62FDB95A03C28BD628143A0B45665802" xlink:to="loc_us-gaap_RelatedPartyDomain_AE27E1C3F03C3C065DBE3A0B4566245A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_AffiliatedEntityMember" xlink:label="loc_srt_AffiliatedEntityMember_09F7601E3874105265573A0B45662EA9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_AE27E1C3F03C3C065DBE3A0B4566245A" xlink:to="loc_srt_AffiliatedEntityMember_09F7601E3874105265573A0B45662EA9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_621F7D0859DEB3B4276E3A0B4566D496" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_C3E3B93EE741591064A63A0B4566DC3A" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_621F7D0859DEB3B4276E3A0B4566D496" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_9280FD18240C52A177413A0B45661533_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_621F7D0859DEB3B4276E3A0B4566D496" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_9280FD18240C52A177413A0B45661533_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_9280FD18240C52A177413A0B45661533" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_621F7D0859DEB3B4276E3A0B4566D496" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_9280FD18240C52A177413A0B45661533" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_SiteLeaseAgreementMember" xlink:label="loc_wlkp_SiteLeaseAgreementMember_6E8C2E46D2E7B7112DA73A0B45666F73" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_9280FD18240C52A177413A0B45661533" xlink:to="loc_wlkp_SiteLeaseAgreementMember_6E8C2E46D2E7B7112DA73A0B45666F73" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_LesseeLeasingArrangementsOperatingLeasesNumber" xlink:label="loc_wlkp_LesseeLeasingArrangementsOperatingLeasesNumber_2818DB233E5AD736DDD03A0B45666BC3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6ED127EE4EFCC5C43D233A0B4566037D" xlink:to="loc_wlkp_LesseeLeasingArrangementsOperatingLeasesNumber_2818DB233E5AD736DDD03A0B45666BC3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseTermOfContract" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_ED7842592A89243A70753A0B45663997" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6ED127EE4EFCC5C43D233A0B4566037D" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_ED7842592A89243A70753A0B45663997" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseAndRentalExpense" xlink:label="loc_us-gaap_LeaseAndRentalExpense_034F2B2814046610867B3A0B4566E8F5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6ED127EE4EFCC5C43D233A0B4566037D" xlink:to="loc_us-gaap_LeaseAndRentalExpense_034F2B2814046610867B3A0B4566E8F5" 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/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:label="loc_us-gaap_SubsequentEventLineItems_A87EDCE09B88F10DAE927ED329D4AAC9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="loc_us-gaap_SubsequentEventTable_ED4A06AA62C2E6BA11E57ED329D4FB95" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_A87EDCE09B88F10DAE927ED329D4AAC9" xlink:to="loc_us-gaap_SubsequentEventTable_ED4A06AA62C2E6BA11E57ED329D4FB95" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_1DB2EC40797D584B1EF97ED329D44CA1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_ED4A06AA62C2E6BA11E57ED329D4FB95" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_1DB2EC40797D584B1EF97ED329D44CA1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_C62FA7EF4F0A186751B67ED966983DB4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1DB2EC40797D584B1EF97ED329D44CA1" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_C62FA7EF4F0A186751B67ED966983DB4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_C62FA7EF4F0A186751B67ED966983DB4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1DB2EC40797D584B1EF97ED329D44CA1" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_C62FA7EF4F0A186751B67ED966983DB4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_BD9B373BFD4ED945EF917ED52B9E4D7A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_C62FA7EF4F0A186751B67ED966983DB4" xlink:to="loc_us-gaap_SubsequentEventMember_BD9B373BFD4ED945EF917ED52B9E4D7A" xlink:type="arc" />
    <link:loc xlink:href="wlkp-20180930.xsd#wlkp_PartnersUnitsMaximumAggregateOfferingAmountATM" xlink:label="loc_wlkp_PartnersUnitsMaximumAggregateOfferingAmountATM_B070D9BFCBD05819B2C27EDBAB37F57B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_A87EDCE09B88F10DAE927ED329D4AAC9" xlink:to="loc_wlkp_PartnersUnitsMaximumAggregateOfferingAmountATM_B070D9BFCBD05819B2C27EDBAB37F57B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/SubsequentEventsSubsequentEvents" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:label="loc_us-gaap_SubsequentEventLineItems_355398F9DA37807573867ED332BE31B3" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="loc_us-gaap_SubsequentEventTable_129F626DEF55D49D4EE87ED332BEC5CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_355398F9DA37807573867ED332BE31B3" xlink:to="loc_us-gaap_SubsequentEventTable_129F626DEF55D49D4EE87ED332BEC5CA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_E6E5E6E1E808F88E382F7ED332BEAA3F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_129F626DEF55D49D4EE87ED332BEC5CA" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_E6E5E6E1E808F88E382F7ED332BEAA3F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_F9E78189312527BE97487ED332BE96EC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_E6E5E6E1E808F88E382F7ED332BEAA3F" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_F9E78189312527BE97487ED332BE96EC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_F9E78189312527BE97487ED332BE96EC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_E6E5E6E1E808F88E382F7ED332BEAA3F" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_F9E78189312527BE97487ED332BE96EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_40413414EE163612099A7ED9B69ED2DE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_F9E78189312527BE97487ED332BE96EC" xlink:to="loc_us-gaap_SubsequentEventMember_40413414EE163612099A7ED9B69ED2DE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsequentEventsTextBlock" xlink:label="loc_us-gaap_SubsequentEventsTextBlock_CBAE43E2F32CC16F9B6A7ED332BE3A79" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_355398F9DA37807573867ED332BE31B3" xlink:to="loc_us-gaap_SubsequentEventsTextBlock_CBAE43E2F32CC16F9B6A7ED332BE3A79" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.westlake.com/role/SubsequentEventsTables" xlink:type="extended" />
  <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>
