<?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.gentex.com/role/AdoptionOfNewAccountingStandards" xlink:href="gntx-20170630.xsd#AdoptionOfNewAccountingStandards" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/AdoptionOfNewAccountingStandardsDetails" xlink:href="gntx-20170630.xsd#AdoptionOfNewAccountingStandardsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/AdoptionOfNewAccountingStandardsPolicies" xlink:href="gntx-20170630.xsd#AdoptionOfNewAccountingStandardsPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/BasisOfPresentation" xlink:href="gntx-20170630.xsd#BasisOfPresentation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncome" xlink:href="gntx-20170630.xsd#ComprehensiveIncome" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeAociRollforwardDetails" xlink:href="gntx-20170630.xsd#ComprehensiveIncomeAociRollforwardDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeReclassificationOutOfAccumulatedOtherComprehensiveIncomeDetails" xlink:href="gntx-20170630.xsd#ComprehensiveIncomeReclassificationOutOfAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeTables" xlink:href="gntx-20170630.xsd#ComprehensiveIncomeTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/Contingencies" xlink:href="gntx-20170630.xsd#Contingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/DebtAndFinancingArrangements" xlink:href="gntx-20170630.xsd#DebtAndFinancingArrangements" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/DebtAndFinancingArrangementsDetails" xlink:href="gntx-20170630.xsd#DebtAndFinancingArrangementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/DebtAndFinancingArrangementsTables" xlink:href="gntx-20170630.xsd#DebtAndFinancingArrangementsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/DocumentAndEntityInformation" xlink:href="gntx-20170630.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/EarningsPerShare" xlink:href="gntx-20170630.xsd#EarningsPerShare" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/EarningsPerShareScheduleOfEarningsPerShareBasicAndDilutedDetails" xlink:href="gntx-20170630.xsd#EarningsPerShareScheduleOfEarningsPerShareBasicAndDilutedDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/EarningsPerShareTables" xlink:href="gntx-20170630.xsd#EarningsPerShareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/Equity" xlink:href="gntx-20170630.xsd#Equity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/EquityDetails" xlink:href="gntx-20170630.xsd#EquityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillAndOtherIntangibleAssets" xlink:href="gntx-20170630.xsd#GoodwillAndOtherIntangibleAssets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillAndOtherIntangibleAssetsDetails" xlink:href="gntx-20170630.xsd#GoodwillAndOtherIntangibleAssetsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfIntangibleAssetsDetails" xlink:href="gntx-20170630.xsd#GoodwillAndOtherIntangibleAssetsScheduleOfIntangibleAssetsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillAndOtherIntangibleAssetsTables" xlink:href="gntx-20170630.xsd#GoodwillAndOtherIntangibleAssetsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/IncomeTaxes" xlink:href="gntx-20170630.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/IncomeTaxesDetails" xlink:href="gntx-20170630.xsd#IncomeTaxesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/Inventories" xlink:href="gntx-20170630.xsd#Inventories" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/InventoriesScheduleOfInventoriesDetails" xlink:href="gntx-20170630.xsd#InventoriesScheduleOfInventoriesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/InventoriesTables" xlink:href="gntx-20170630.xsd#InventoriesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/Investments" xlink:href="gntx-20170630.xsd#Investments" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsInvestmentsClassifiedByContractualMaturityDateDetails" xlink:href="gntx-20170630.xsd#InvestmentsInvestmentsClassifiedByContractualMaturityDateDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleOfAmortizedCostUnrealizedGainsAndLossesAndMarketValueOfInvestmentSecuritiesDetails" xlink:href="gntx-20170630.xsd#InvestmentsScheduleOfAmortizedCostUnrealizedGainsAndLossesAndMarketValueOfInvestmentSecuritiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleOfUnrealizedLossOnInvestmentsDetails" xlink:href="gntx-20170630.xsd#InvestmentsScheduleOfUnrealizedLossOnInvestmentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsTables" xlink:href="gntx-20170630.xsd#InvestmentsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/SegmentReporting" xlink:href="gntx-20170630.xsd#SegmentReporting" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/SegmentReportingScheduleOfAutomotiveAndOtherSegmentReportingDetails" xlink:href="gntx-20170630.xsd#SegmentReportingScheduleOfAutomotiveAndOtherSegmentReportingDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/SegmentReportingTables" xlink:href="gntx-20170630.xsd#SegmentReportingTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlans" xlink:href="gntx-20170630.xsd#StockBasedCompensationPlans" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansNarrativeDetails" xlink:href="gntx-20170630.xsd#StockBasedCompensationPlansNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansTables" xlink:href="gntx-20170630.xsd#StockBasedCompensationPlansTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansWeightedAverageAssumptionsForEsopDetails" xlink:href="gntx-20170630.xsd#StockBasedCompensationPlansWeightedAverageAssumptionsForEsopDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/UnauditedCondensedConsolidatedBalanceSheets" xlink:href="gntx-20170630.xsd#UnauditedCondensedConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsOfCashFlows" xlink:href="gntx-20170630.xsd#UnauditedCondensedConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsOfComprehensiveIncome" xlink:href="gntx-20170630.xsd#UnauditedCondensedConsolidatedStatementsOfComprehensiveIncome" xlink:type="simple" />
  <link:roleRef roleURI="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsOfIncome" xlink:href="gntx-20170630.xsd#UnauditedCondensedConsolidatedStatementsOfIncome" 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.gentex.com/role/AdoptionOfNewAccountingStandards" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/AdoptionOfNewAccountingStandardsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F7FF24EE48DF63AA984FA95D14A60CA7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_86CFEC76E8EFBAA91A97A95D14A677A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F7FF24EE48DF63AA984FA95D14A60CA7" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_86CFEC76E8EFBAA91A97A95D14A677A3" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_749050B05F54E45CE169A95D14A68A53" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_86CFEC76E8EFBAA91A97A95D14A677A3" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_749050B05F54E45CE169A95D14A68A53" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_A1AEAC9199135CFD6478A95D14A6C2EB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_749050B05F54E45CE169A95D14A68A53" xlink:to="loc_us-gaap_TypeOfAdoptionMember_A1AEAC9199135CFD6478A95D14A6C2EB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_A1AEAC9199135CFD6478A95D14A6C2EB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_749050B05F54E45CE169A95D14A68A53" xlink:to="loc_us-gaap_TypeOfAdoptionMember_A1AEAC9199135CFD6478A95D14A6C2EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountingStandardsUpdate201609Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201609Member_DB722E1BFD7CABEC09E1A95D14A64DC0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_A1AEAC9199135CFD6478A95D14A6C2EB" xlink:to="loc_us-gaap_AccountingStandardsUpdate201609Member_DB722E1BFD7CABEC09E1A95D14A64DC0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_798D54FE2C4CF5DE082DA95D14A6A391" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_86CFEC76E8EFBAA91A97A95D14A677A3" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_798D54FE2C4CF5DE082DA95D14A6A391" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_650CA81FD3DA4AE0B9CBA95D14A614DF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_798D54FE2C4CF5DE082DA95D14A6A391" xlink:to="loc_us-gaap_EquityComponentDomain_650CA81FD3DA4AE0B9CBA95D14A614DF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_650CA81FD3DA4AE0B9CBA95D14A614DF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_798D54FE2C4CF5DE082DA95D14A6A391" xlink:to="loc_us-gaap_EquityComponentDomain_650CA81FD3DA4AE0B9CBA95D14A614DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_392819032DA41B12C7D4A95D14A68687" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_650CA81FD3DA4AE0B9CBA95D14A614DF" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_392819032DA41B12C7D4A95D14A68687" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_EffectiveIncomeTaxRateReconciliationSharebasedCompensationExcessTaxBenefitAmount" xlink:label="loc_gntx_EffectiveIncomeTaxRateReconciliationSharebasedCompensationExcessTaxBenefitAmount_1EB8439E5829D04B8A95A95D14A61EF4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F7FF24EE48DF63AA984FA95D14A60CA7" xlink:to="loc_gntx_EffectiveIncomeTaxRateReconciliationSharebasedCompensationExcessTaxBenefitAmount_1EB8439E5829D04B8A95A95D14A61EF4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentToAdditionalPaidInCapitalIncomeTaxEffectFromShareBasedCompensationNet" xlink:label="loc_us-gaap_AdjustmentToAdditionalPaidInCapitalIncomeTaxEffectFromShareBasedCompensationNet_760BB2BB39CEEC62562EA95D14A79A50" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F7FF24EE48DF63AA984FA95D14A60CA7" xlink:to="loc_us-gaap_AdjustmentToAdditionalPaidInCapitalIncomeTaxEffectFromShareBasedCompensationNet_760BB2BB39CEEC62562EA95D14A79A50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation_5B19FBB9838F89C568FEA95D14A7DC94" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F7FF24EE48DF63AA984FA95D14A60CA7" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation_5B19FBB9838F89C568FEA95D14A7DC94" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalIncomeTaxDeficiencyFromShareBasedCompensation" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalIncomeTaxDeficiencyFromShareBasedCompensation_C7B4C3463F3A1CBAC742A95D14A76BB8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F7FF24EE48DF63AA984FA95D14A60CA7" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalIncomeTaxDeficiencyFromShareBasedCompensation_C7B4C3463F3A1CBAC742A95D14A76BB8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_5D2EC3F0B600B5D12047A95D14A73954" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F7FF24EE48DF63AA984FA95D14A60CA7" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_5D2EC3F0B600B5D12047A95D14A73954" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_86788B6A65B69789371BA95D14A7AE66" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F7FF24EE48DF63AA984FA95D14A60CA7" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_86788B6A65B69789371BA95D14A7AE66" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfChangeOnBasicEarningsPerShare" xlink:label="loc_us-gaap_NewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfChangeOnBasicEarningsPerShare_26AC0C72C2D0A1F71F66A95D14A7D873" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_F7FF24EE48DF63AA984FA95D14A60CA7" xlink:to="loc_us-gaap_NewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfChangeOnBasicEarningsPerShare_26AC0C72C2D0A1F71F66A95D14A7D873" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AdoptionOfNewAccountingStandardsPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/BasisOfPresentation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncome" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeAociRollforwardDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_2C1EF67C7CD3CC0DA65956F00EE4A565" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_35FF4B6F753A8F01DF7656F00EE34462" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_2C1EF67C7CD3CC0DA65956F00EE4A565" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_35FF4B6F753A8F01DF7656F00EE34462" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_194CD956EABC0CFCC97056F00EE3803C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_35FF4B6F753A8F01DF7656F00EE34462" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_194CD956EABC0CFCC97056F00EE3803C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_416D55633A036C487B5D56F00EE3E3C6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_194CD956EABC0CFCC97056F00EE3803C" xlink:to="loc_us-gaap_EquityComponentDomain_416D55633A036C487B5D56F00EE3E3C6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_416D55633A036C487B5D56F00EE3E3C6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_194CD956EABC0CFCC97056F00EE3803C" xlink:to="loc_us-gaap_EquityComponentDomain_416D55633A036C487B5D56F00EE3E3C6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_978FCE00D5239B2430EF56F00EE49C6D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_416D55633A036C487B5D56F00EE3E3C6" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_978FCE00D5239B2430EF56F00EE49C6D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_D017BB68449505EB835A56F00EE476A0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_416D55633A036C487B5D56F00EE3E3C6" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_D017BB68449505EB835A56F00EE476A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember" xlink:label="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_0358A60E8E22AD07A78856F00EE43CA3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_416D55633A036C487B5D56F00EE3E3C6" xlink:to="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_0358A60E8E22AD07A78856F00EE43CA3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_70FBE101369F6A1DEDED56F00EE4FE3A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_2C1EF67C7CD3CC0DA65956F00EE4A565" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_70FBE101369F6A1DEDED56F00EE4FE3A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_FEB85F0B3E39ECB6BDD556F00EE46474" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_70FBE101369F6A1DEDED56F00EE4FE3A" xlink:to="loc_us-gaap_StockholdersEquity_FEB85F0B3E39ECB6BDD556F00EE46474" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_50535C94E95BE23B122956F00EE47E82" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_70FBE101369F6A1DEDED56F00EE4FE3A" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_50535C94E95BE23B122956F00EE47E82" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_CCCB50C617F4B136B15256F00EE4CBDE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_70FBE101369F6A1DEDED56F00EE4FE3A" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_CCCB50C617F4B136B15256F00EE4CBDE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_A563F30BC3326705732A56F00EE48728" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_70FBE101369F6A1DEDED56F00EE4FE3A" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_A563F30BC3326705732A56F00EE48728" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AociTaxAttributableToParent" xlink:label="loc_us-gaap_AociTaxAttributableToParent_0AFB2DB73DC6F771D0BB56F00EE94893" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_70FBE101369F6A1DEDED56F00EE4FE3A" xlink:to="loc_us-gaap_AociTaxAttributableToParent_0AFB2DB73DC6F771D0BB56F00EE94893" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeReclassificationOutOfAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_23DEA3746608B332C013A95D143B150C" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_E00F6C2AECC7C055A339A95D143AFF75" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_23DEA3746608B332C013A95D143B150C" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_E00F6C2AECC7C055A339A95D143AFF75" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_988B576D37CD245D727AA95D143A1456" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_E00F6C2AECC7C055A339A95D143AFF75" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_988B576D37CD245D727AA95D143A1456" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_4114FF7C86210DE84094A95D143A5364_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_988B576D37CD245D727AA95D143A1456" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_4114FF7C86210DE84094A95D143A5364_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_4114FF7C86210DE84094A95D143A5364" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_988B576D37CD245D727AA95D143A1456" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_4114FF7C86210DE84094A95D143A5364" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_2AE625E80E1F2CE2F6E6A95D143A4EE5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_4114FF7C86210DE84094A95D143A5364" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_2AE625E80E1F2CE2F6E6A95D143A4EE5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_C67A81297EBDC4621E68A95D143A5F9B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_E00F6C2AECC7C055A339A95D143AFF75" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_C67A81297EBDC4621E68A95D143A5F9B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_FDDD9B2911C936BFEF41A95D143A8959_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_C67A81297EBDC4621E68A95D143A5F9B" xlink:to="loc_us-gaap_EquityComponentDomain_FDDD9B2911C936BFEF41A95D143A8959_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_FDDD9B2911C936BFEF41A95D143A8959" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_C67A81297EBDC4621E68A95D143A5F9B" xlink:to="loc_us-gaap_EquityComponentDomain_FDDD9B2911C936BFEF41A95D143A8959" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_4D2E731BB77DA7D76F96A95D143AAC9C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_FDDD9B2911C936BFEF41A95D143A8959" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_4D2E731BB77DA7D76F96A95D143AAC9C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember" xlink:label="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_F10734EBE5781F20B17DA95D143AC9BA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_FDDD9B2911C936BFEF41A95D143A8959" xlink:to="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_F10734EBE5781F20B17DA95D143AC9BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GainLossOnInvestmentsExcludingOtherThanTemporaryImpairments" xlink:label="loc_us-gaap_GainLossOnInvestmentsExcludingOtherThanTemporaryImpairments_1FD5DF25166D77A4F41DA95D143B60DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_23DEA3746608B332C013A95D143B150C" xlink:to="loc_us-gaap_GainLossOnInvestmentsExcludingOtherThanTemporaryImpairments_1FD5DF25166D77A4F41DA95D143B60DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_9458F81DA6F68D82D283A95D143BADCF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_23DEA3746608B332C013A95D143B150C" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_9458F81DA6F68D82D283A95D143BADCF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_E3481EF0F407C00DE995A95D143B3C31" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_23DEA3746608B332C013A95D143B150C" xlink:to="loc_us-gaap_ProfitLoss_E3481EF0F407C00DE995A95D143B3C31" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/Contingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/DebtAndFinancingArrangements" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/DebtAndFinancingArrangementsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_D581132553FE67CD37408573E23F512D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_DebtInstrumentTable_D581132553FE67CD37408573E23F512D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_2576E21381D53DB864CC8573E23FA6E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_D581132553FE67CD37408573E23F512D" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_2576E21381D53DB864CC8573E23FA6E0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_72A8B82F7DD7BDB6C2468573E23F9C6F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2576E21381D53DB864CC8573E23FA6E0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_72A8B82F7DD7BDB6C2468573E23F9C6F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_72A8B82F7DD7BDB6C2468573E23F9C6F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2576E21381D53DB864CC8573E23FA6E0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_72A8B82F7DD7BDB6C2468573E23F9C6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_D0135B36975C2615B59E8573E23F4442" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_72A8B82F7DD7BDB6C2468573E23F9C6F" xlink:to="loc_us-gaap_LineOfCreditMember_D0135B36975C2615B59E8573E23F4442" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_0FA94B7666D5CC9F1ADB8573E23F4DA4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditMember_D0135B36975C2615B59E8573E23F4442" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_0FA94B7666D5CC9F1ADB8573E23F4DA4" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_TermLoanMember" xlink:label="loc_gntx_TermLoanMember_607A6CF5C414B5051EFA8573E23FDEF0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditMember_D0135B36975C2615B59E8573E23F4442" xlink:to="loc_gntx_TermLoanMember_607A6CF5C414B5051EFA8573E23FDEF0" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_SwingLoansMember" xlink:label="loc_gntx_SwingLoansMember_22ED4C826055DBD984C48573E23FDE12" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditMember_D0135B36975C2615B59E8573E23F4442" xlink:to="loc_gntx_SwingLoansMember_22ED4C826055DBD984C48573E23FDE12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LetterOfCreditMember" xlink:label="loc_us-gaap_LetterOfCreditMember_4FEB7D04E42EF1E744708573E23FC9F1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditMember_D0135B36975C2615B59E8573E23F4442" xlink:to="loc_us-gaap_LetterOfCreditMember_4FEB7D04E42EF1E744708573E23FC9F1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShortTermDebtTypeAxis" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_03CCA63AF12B0A1D155E8573E2408450" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_D581132553FE67CD37408573E23F512D" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_03CCA63AF12B0A1D155E8573E2408450" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShortTermDebtTypeDomain" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_8C4DE04E64F6A72D1F708573E2406275_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_03CCA63AF12B0A1D155E8573E2408450" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_8C4DE04E64F6A72D1F708573E2406275_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShortTermDebtTypeDomain" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_8C4DE04E64F6A72D1F708573E2406275" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_03CCA63AF12B0A1D155E8573E2408450" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_8C4DE04E64F6A72D1F708573E2406275" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_76ED83A18215D84483878573E240AFFF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_8C4DE04E64F6A72D1F708573E2406275" xlink:to="loc_us-gaap_LineOfCreditMember_76ED83A18215D84483878573E240AFFF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ExtinguishmentOfDebtAxis" xlink:label="loc_us-gaap_ExtinguishmentOfDebtAxis_0498FA7C9FA2280B697C8573E240A457" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_D581132553FE67CD37408573E23F512D" xlink:to="loc_us-gaap_ExtinguishmentOfDebtAxis_0498FA7C9FA2280B697C8573E240A457" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ExtinguishmentOfDebtTypeDomain" xlink:label="loc_us-gaap_ExtinguishmentOfDebtTypeDomain_6287A5171EE84B502D738573E240E193_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ExtinguishmentOfDebtAxis_0498FA7C9FA2280B697C8573E240A457" xlink:to="loc_us-gaap_ExtinguishmentOfDebtTypeDomain_6287A5171EE84B502D738573E240E193_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ExtinguishmentOfDebtTypeDomain" xlink:label="loc_us-gaap_ExtinguishmentOfDebtTypeDomain_6287A5171EE84B502D738573E240E193" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ExtinguishmentOfDebtAxis_0498FA7C9FA2280B697C8573E240A457" xlink:to="loc_us-gaap_ExtinguishmentOfDebtTypeDomain_6287A5171EE84B502D738573E240E193" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_TermLoanandRevolvingFacilityMember" xlink:label="loc_gntx_TermLoanandRevolvingFacilityMember_F85A775C8AE936D3AB178573E2403D20" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ExtinguishmentOfDebtTypeDomain_6287A5171EE84B502D738573E240E193" xlink:to="loc_gntx_TermLoanandRevolvingFacilityMember_F85A775C8AE936D3AB178573E2403D20" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_2A389A28B94EF7292C1D8573E240A60E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ExtinguishmentOfDebtTypeDomain_6287A5171EE84B502D738573E240E193" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_2A389A28B94EF7292C1D8573E240A60E" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_TermLoanMember" xlink:label="loc_gntx_TermLoanMember_3916FD25A3EA9DCE05138573E240A755" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ExtinguishmentOfDebtTypeDomain_6287A5171EE84B502D738573E240E193" xlink:to="loc_gntx_TermLoanMember_3916FD25A3EA9DCE05138573E240A755" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="loc_us-gaap_VariableRateAxis_BE53563BF88C0354DBFD8573E2406646" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_D581132553FE67CD37408573E23F512D" xlink:to="loc_us-gaap_VariableRateAxis_BE53563BF88C0354DBFD8573E2406646" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_E8B736E0825889DD8B758573E2418BE4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_BE53563BF88C0354DBFD8573E2406646" xlink:to="loc_us-gaap_VariableRateDomain_E8B736E0825889DD8B758573E2418BE4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_E8B736E0825889DD8B758573E2418BE4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_BE53563BF88C0354DBFD8573E2406646" xlink:to="loc_us-gaap_VariableRateDomain_E8B736E0825889DD8B758573E2418BE4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_638985720B1F38E024478573E241A009" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_E8B736E0825889DD8B758573E2418BE4" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_638985720B1F38E024478573E241A009" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_B86EAE1462B02462FA9A8573E2410076" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_D581132553FE67CD37408573E23F512D" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_B86EAE1462B02462FA9A8573E2410076" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_4EBBD9BC23E497DAD0588573E241F887_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_B86EAE1462B02462FA9A8573E2410076" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_4EBBD9BC23E497DAD0588573E241F887_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_4EBBD9BC23E497DAD0588573E241F887" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_B86EAE1462B02462FA9A8573E2410076" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_4EBBD9BC23E497DAD0588573E241F887" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_OtherNetMember" xlink:label="loc_gntx_OtherNetMember_82F1EC0E07EC2EEF41918573E2410218" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4EBBD9BC23E497DAD0588573E241F887" xlink:to="loc_gntx_OtherNetMember_82F1EC0E07EC2EEF41918573E2410218" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_D105D91A9DC2957618588573E241ED0E" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_D581132553FE67CD37408573E23F512D" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_D105D91A9DC2957618588573E241ED0E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_F5AA3E1C74729328ACA98573E2412F02_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_D105D91A9DC2957618588573E241ED0E" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_F5AA3E1C74729328ACA98573E2412F02_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_F5AA3E1C74729328ACA98573E2412F02" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_D105D91A9DC2957618588573E241ED0E" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_F5AA3E1C74729328ACA98573E2412F02" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestRateSwapMember" xlink:label="loc_us-gaap_InterestRateSwapMember_33B7DFBCD3634A2F183A8573E241D9F3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_F5AA3E1C74729328ACA98573E2412F02" xlink:to="loc_us-gaap_InterestRateSwapMember_33B7DFBCD3634A2F183A8573E241D9F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_00274E01242EC87353E98573E241C508" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_D581132553FE67CD37408573E23F512D" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_00274E01242EC87353E98573E241C508" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_B98F26ED0987B03F1CA98573E2411C57_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_00274E01242EC87353E98573E241C508" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_B98F26ED0987B03F1CA98573E2411C57_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_B98F26ED0987B03F1CA98573E2411C57" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_00274E01242EC87353E98573E241C508" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_B98F26ED0987B03F1CA98573E2411C57" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_3B77F7A0DB4ED86307F88573E241C499" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_B98F26ED0987B03F1CA98573E2411C57" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_3B77F7A0DB4ED86307F88573E241C499" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_212572A30F55127EDC498573E242D7DE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_212572A30F55127EDC498573E242D7DE" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount" xlink:label="loc_gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount_D32B45ACE5CD4D4F3F3A8573E2429046" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount_D32B45ACE5CD4D4F3F3A8573E2429046" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ExtinguishmentOfDebtAmount" xlink:label="loc_us-gaap_ExtinguishmentOfDebtAmount_9D6F1D9C9B74B11F64068573E2427C09" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_ExtinguishmentOfDebtAmount_9D6F1D9C9B74B11F64068573E2427C09" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShortTermBorrowings" xlink:label="loc_us-gaap_ShortTermBorrowings_EF79B9B72BD9B3C4EDC58573E242D32B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_ShortTermBorrowings_EF79B9B72BD9B3C4EDC58573E242D32B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongTermDebt" xlink:label="loc_us-gaap_LongTermDebt_780B8C1583149257D4578573E2422614" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_LongTermDebt_780B8C1583149257D4578573E2422614" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentAnnualPrincipalPayment" xlink:label="loc_us-gaap_DebtInstrumentAnnualPrincipalPayment_406A2CB57CF934B584E78573E2424401" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_DebtInstrumentAnnualPrincipalPayment_406A2CB57CF934B584E78573E2424401" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_2835901656BB0141F13A8573E2428247" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_2835901656BB0141F13A8573E2428247" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsOfFinancingCosts" xlink:label="loc_us-gaap_PaymentsOfFinancingCosts_1838487F950A90A442CE8573E2424E8F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_PaymentsOfFinancingCosts_1838487F950A90A442CE8573E2424E8F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeAmountOfHedgedItem" xlink:label="loc_us-gaap_DerivativeAmountOfHedgedItem_AD505C1F6CF1399C93A68573E24207E8" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_DerivativeAmountOfHedgedItem_AD505C1F6CF1399C93A68573E24207E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeLiabilityNotionalAmount" xlink:label="loc_us-gaap_DerivativeLiabilityNotionalAmount_960B2057CA692F9300418573E242D8E8" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_DerivativeLiabilityNotionalAmount_960B2057CA692F9300418573E242D8E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeFixedInterestRate" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_F71262AA78E1B47309A78573E2421AD4" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_F71262AA78E1B47309A78573E2421AD4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpenseDebt" xlink:label="loc_us-gaap_InterestExpenseDebt_6615D3B2FEAC5399ED0A8573E2421FC6" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_InterestExpenseDebt_6615D3B2FEAC5399ED0A8573E2421FC6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsFairValueDisclosureAbstract" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_601A8EF3A7E7F17420618573E24216C0" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_601A8EF3A7E7F17420618573E24216C0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeAssets" xlink:label="loc_us-gaap_DerivativeAssets_DC8C3EDB5CD2B5F689BF8573E2432BEA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_601A8EF3A7E7F17420618573E24216C0" xlink:to="loc_us-gaap_DerivativeAssets_DC8C3EDB5CD2B5F689BF8573E2432BEA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FinancialLiabilitiesFairValueDisclosureAbstract" xlink:label="loc_us-gaap_FinancialLiabilitiesFairValueDisclosureAbstract_2647BE6780121B69F8F58573E2432969" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_us-gaap_FinancialLiabilitiesFairValueDisclosureAbstract_2647BE6780121B69F8F58573E2432969" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DerivativeLiabilities" xlink:label="loc_us-gaap_DerivativeLiabilities_561BF5D55E35333C97A18573E2431A81" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialLiabilitiesFairValueDisclosureAbstract_2647BE6780121B69F8F58573E2432969" xlink:to="loc_us-gaap_DerivativeLiabilities_561BF5D55E35333C97A18573E2431A81" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_EffectofOnePercentagePointIncreaseonBorrowingRatetoInterestExpense" xlink:label="loc_gntx_EffectofOnePercentagePointIncreaseonBorrowingRatetoInterestExpense_CFB41172D7FE1E634CDC8573E24343E0" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_C2A02C8925DA64805C748573E242AC10" xlink:to="loc_gntx_EffectofOnePercentagePointIncreaseonBorrowingRatetoInterestExpense_CFB41172D7FE1E634CDC8573E24343E0" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.gentex.com/role/DebtAndFinancingArrangementsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/DocumentAndEntityInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/EarningsPerShare" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/EarningsPerShareScheduleOfEarningsPerShareBasicAndDilutedDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/EarningsPerShareTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/Equity" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/EquityDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillAndOtherIntangibleAssets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillAndOtherIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:href="gntx-20170630.xsd#gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems" xlink:label="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:type="locator" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable" xlink:label="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable_205125B3289200D3032F56F00FAFFAA4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:to="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable_205125B3289200D3032F56F00FAFFAA4" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_80EF528CB63F9A6FDA4556F00FAF036B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable_205125B3289200D3032F56F00FAFFAA4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_80EF528CB63F9A6FDA4556F00FAF036B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47C819DA07DB9AD17A6856F00FAFC58C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_80EF528CB63F9A6FDA4556F00FAF036B" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47C819DA07DB9AD17A6856F00FAFC58C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47C819DA07DB9AD17A6856F00FAFC58C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_80EF528CB63F9A6FDA4556F00FAF036B" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47C819DA07DB9AD17A6856F00FAFC58C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PatentsMember" xlink:label="loc_us-gaap_PatentsMember_FB6B1A8A651AFE8AECAA56F00FAFCCE1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47C819DA07DB9AD17A6856F00FAFC58C" xlink:to="loc_us-gaap_PatentsMember_FB6B1A8A651AFE8AECAA56F00FAFCCE1" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_PatentsandOtherIntangibleAssetsMember" xlink:label="loc_gntx_PatentsandOtherIntangibleAssetsMember_44DBB9B207ECDEEB925956F00FB41702" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47C819DA07DB9AD17A6856F00FAFC58C" xlink:to="loc_gntx_PatentsandOtherIntangibleAssetsMember_44DBB9B207ECDEEB925956F00FB41702" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_4AA427BE891983F11CB256F00FB463D1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable_205125B3289200D3032F56F00FAFFAA4" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_4AA427BE891983F11CB256F00FB463D1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4303D032C9A5F8FCB60A56F00FB4079F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_4AA427BE891983F11CB256F00FB463D1" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4303D032C9A5F8FCB60A56F00FB4079F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4303D032C9A5F8FCB60A56F00FB4079F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_4AA427BE891983F11CB256F00FB463D1" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4303D032C9A5F8FCB60A56F00FB4079F" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_HomeLinkMember" xlink:label="loc_gntx_HomeLinkMember_A0C690C7FDA03125027A56F00FB4CF5D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4303D032C9A5F8FCB60A56F00FB4079F" xlink:to="loc_gntx_HomeLinkMember_A0C690C7FDA03125027A56F00FB4CF5D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_10431D63E12FF96640CB56F00FB505D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:to="loc_us-gaap_Goodwill_10431D63E12FF96640CB56F00FB505D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_4C7224EEFF3F8223E2B556F00FB57AB8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_4C7224EEFF3F8223E2B556F00FB57AB8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_E8A1D31671133120D85856F00FB57517" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_E8A1D31671133120D85856F00FB57517" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_A4ED6BA0C7E75B57172B56F00FB573C5" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_A4ED6BA0C7E75B57172B56F00FB573C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_50840B41A82037E2FAB356F00FB5B914" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_50840B41A82037E2FAB356F00FB5B914" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_8636B2DF415DC503FB3156F00FB5AD46" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_8636B2DF415DC503FB3156F00FB5AD46" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_0051D77C007576DEE62E56F00FB5C51E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_0051D77C007576DEE62E56F00FB5C51E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_5B07247250C7A124E96A56F00FB5EF2B" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_5B07247250C7A124E96A56F00FB5EF2B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive_D1A380C555E39617431656F00FB58A0F" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_FDC92C66705D6354176056F00FB491DC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive_D1A380C555E39617431656F00FB58A0F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillAndOtherIntangibleAssetsScheduleOfIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:href="gntx-20170630.xsd#gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems" xlink:label="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_4B9CF0AFCA9005F5008A57EF3A50F301" xlink:type="locator" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable" xlink:label="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable_1AC964D6A529C50114FC57EF3A4FA0D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_4B9CF0AFCA9005F5008A57EF3A50F301" xlink:to="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable_1AC964D6A529C50114FC57EF3A4FA0D3" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_9D94262AAC07E959C20057EF3A4F5DE9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable_1AC964D6A529C50114FC57EF3A4FA0D3" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_9D94262AAC07E959C20057EF3A4F5DE9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6335A662A9A12C79600F57EF3A4F7A21_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_9D94262AAC07E959C20057EF3A4F5DE9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6335A662A9A12C79600F57EF3A4F7A21_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6335A662A9A12C79600F57EF3A4F7A21" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_9D94262AAC07E959C20057EF3A4F5DE9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6335A662A9A12C79600F57EF3A4F7A21" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_HomeLinkMember" xlink:label="loc_gntx_HomeLinkMember_538C2A578D6758ADF7DE57EF3A50E52D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6335A662A9A12C79600F57EF3A4F7A21" xlink:to="loc_gntx_HomeLinkMember_538C2A578D6758ADF7DE57EF3A50E52D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_31458DDAEA6A7FA5055257EF3A50475A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable_1AC964D6A529C50114FC57EF3A4FA0D3" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_31458DDAEA6A7FA5055257EF3A50475A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_1E7D9BC5A99E5FAE740057EF3A509822_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_31458DDAEA6A7FA5055257EF3A50475A" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_1E7D9BC5A99E5FAE740057EF3A509822_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_1E7D9BC5A99E5FAE740057EF3A509822" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_31458DDAEA6A7FA5055257EF3A50475A" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_1E7D9BC5A99E5FAE740057EF3A509822" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TrademarksAndTradeNamesMember" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_E72CA5D9DA2E09ADC64657EF3A5019F0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_1E7D9BC5A99E5FAE740057EF3A509822" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_E72CA5D9DA2E09ADC64657EF3A5019F0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LicensingAgreementsMember" xlink:label="loc_us-gaap_LicensingAgreementsMember_166147D9F0D9892EAF1F57EF3A502EF8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_1E7D9BC5A99E5FAE740057EF3A509822" xlink:to="loc_us-gaap_LicensingAgreementsMember_166147D9F0D9892EAF1F57EF3A502EF8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_9C553DC98C03EB35D5B057EF3A50558C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable_1AC964D6A529C50114FC57EF3A4FA0D3" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_9C553DC98C03EB35D5B057EF3A50558C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1F43A4D1155E6E35822C57EF3A506374_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_9C553DC98C03EB35D5B057EF3A50558C" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1F43A4D1155E6E35822C57EF3A506374_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1F43A4D1155E6E35822C57EF3A506374" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_9C553DC98C03EB35D5B057EF3A50558C" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1F43A4D1155E6E35822C57EF3A506374" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PatentsMember" xlink:label="loc_us-gaap_PatentsMember_C4D356627B70610D4B5057EF3A506D47" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1F43A4D1155E6E35822C57EF3A506374" xlink:to="loc_us-gaap_PatentsMember_C4D356627B70610D4B5057EF3A506D47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_A8ADA04F60E3448669F257EF3A508D2E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1F43A4D1155E6E35822C57EF3A506374" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_A8ADA04F60E3448669F257EF3A508D2E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CustomerContractsMember" xlink:label="loc_us-gaap_CustomerContractsMember_51646B1AF0B26CDF8B8C57EF3A503B0E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1F43A4D1155E6E35822C57EF3A506374" xlink:to="loc_us-gaap_CustomerContractsMember_51646B1AF0B26CDF8B8C57EF3A503B0E" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_PatentsandOtherIntangibleAssetsMember" xlink:label="loc_gntx_PatentsandOtherIntangibleAssetsMember_8AA5314B91E611BE362157EF3A504868" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1F43A4D1155E6E35822C57EF3A506374" xlink:to="loc_gntx_PatentsandOtherIntangibleAssetsMember_8AA5314B91E611BE362157EF3A504868" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_CB74101E75CABFA964CD57EF3A50597C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsTable_1AC964D6A529C50114FC57EF3A4FA0D3" xlink:to="loc_us-gaap_RangeAxis_CB74101E75CABFA964CD57EF3A50597C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_6F0BF831424C26BFAAC957EF3A5026AD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_CB74101E75CABFA964CD57EF3A50597C" xlink:to="loc_us-gaap_RangeMember_6F0BF831424C26BFAAC957EF3A5026AD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_6F0BF831424C26BFAAC957EF3A5026AD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_CB74101E75CABFA964CD57EF3A50597C" xlink:to="loc_us-gaap_RangeMember_6F0BF831424C26BFAAC957EF3A5026AD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_9E04785CC3CCAF36B76D57EF3A50D94E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_6F0BF831424C26BFAAC957EF3A5026AD" xlink:to="loc_us-gaap_MinimumMember_9E04785CC3CCAF36B76D57EF3A50D94E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_2D9D782581918A6F8AED57EF3A511EB7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_4B9CF0AFCA9005F5008A57EF3A50F301" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_2D9D782581918A6F8AED57EF3A511EB7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_6B62CBFFCF7D81028CC457EF3A513299" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_4B9CF0AFCA9005F5008A57EF3A50F301" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_6B62CBFFCF7D81028CC457EF3A513299" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_3C75401464976529F6E457EF3A51A511" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_4B9CF0AFCA9005F5008A57EF3A50F301" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_3C75401464976529F6E457EF3A51A511" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_5F3FFD9C36B91DF2A6A357EF3A5191A3" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_4B9CF0AFCA9005F5008A57EF3A50F301" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_5F3FFD9C36B91DF2A6A357EF3A5191A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_794297EADEA79CDFB58957EF3A518590" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_4B9CF0AFCA9005F5008A57EF3A50F301" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_794297EADEA79CDFB58957EF3A518590" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_5C6A78A75728F98022E257EF3A5179A4" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_4B9CF0AFCA9005F5008A57EF3A50F301" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_5C6A78A75728F98022E257EF3A5179A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_DF9856D1228DFC4F6AD957EF3A5139E0" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_ScheduleofFiniteLivedandIndefiniteLivedIntangibleAssetsLineItems_4B9CF0AFCA9005F5008A57EF3A50F301" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_DF9856D1228DFC4F6AD957EF3A5139E0" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillAndOtherIntangibleAssetsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/IncomeTaxes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/IncomeTaxesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/Inventories" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/InventoriesScheduleOfInventoriesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/InventoriesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/Investments" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsInvestmentsClassifiedByContractualMaturityDateDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_7D66C9DE7A377413589356F00F36082B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_60C6A4ADFB3E0332BB0956F00F3641DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_7D66C9DE7A377413589356F00F36082B" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_60C6A4ADFB3E0332BB0956F00F3641DA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_8D60C6E036B3C2DD786556F00F36975F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_60C6A4ADFB3E0332BB0956F00F3641DA" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_8D60C6E036B3C2DD786556F00F36975F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_EF8D87A256B8B441D47F56F00F3633C5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_8D60C6E036B3C2DD786556F00F36975F" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_EF8D87A256B8B441D47F56F00F3633C5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_EF8D87A256B8B441D47F56F00F3633C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_8D60C6E036B3C2DD786556F00F36975F" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_EF8D87A256B8B441D47F56F00F3633C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FixedIncomeSecuritiesMember" xlink:label="loc_us-gaap_FixedIncomeSecuritiesMember_8A8C8F9E252DB5923FA256F00F360B72" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_EF8D87A256B8B441D47F56F00F3633C5" xlink:to="loc_us-gaap_FixedIncomeSecuritiesMember_8A8C8F9E252DB5923FA256F00F360B72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_A02BBB793FFDA4468A1756F00F36E03F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_7D66C9DE7A377413589356F00F36082B" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_A02BBB793FFDA4468A1756F00F36E03F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_93B6529F577B096EFE8B56F00F36676F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_7D66C9DE7A377413589356F00F36082B" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_93B6529F577B096EFE8B56F00F36676F" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_AvailableforsaleSecuritiesDebtMaturitiesafterFiveYearsFairValue" xlink:label="loc_gntx_AvailableforsaleSecuritiesDebtMaturitiesafterFiveYearsFairValue_8C7744FAA3605576B8CB56F00F37230B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_7D66C9DE7A377413589356F00F36082B" xlink:to="loc_gntx_AvailableforsaleSecuritiesDebtMaturitiesafterFiveYearsFairValue_8C7744FAA3605576B8CB56F00F37230B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_AF8EE2A541EC1BD0B08456F00F37BB96" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_7D66C9DE7A377413589356F00F36082B" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_AF8EE2A541EC1BD0B08456F00F37BB96" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleOfAmortizedCostUnrealizedGainsAndLossesAndMarketValueOfInvestmentSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A9612B18F794C2E765FE80D4423B7C37" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd#invest_InvestmentTable" xlink:label="loc_invest_InvestmentTable_49E0BD00D2959DEBB96280D4423AFDBD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A9612B18F794C2E765FE80D4423B7C37" xlink:to="loc_invest_InvestmentTable_49E0BD00D2959DEBB96280D4423AFDBD" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_DBA3DC9117CDFB82AD9C80D4423AC2D4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_invest_InvestmentTable_49E0BD00D2959DEBB96280D4423AFDBD" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_DBA3DC9117CDFB82AD9C80D4423AC2D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A4AB84EC01782D65E20880D4423A8267_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_DBA3DC9117CDFB82AD9C80D4423AC2D4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A4AB84EC01782D65E20880D4423A8267_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A4AB84EC01782D65E20880D4423A8267" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_DBA3DC9117CDFB82AD9C80D4423AC2D4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A4AB84EC01782D65E20880D4423A8267" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_1E8A72BE62F6C2A5E21180D4423AB94C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A4AB84EC01782D65E20880D4423A8267" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_1E8A72BE62F6C2A5E21180D4423AB94C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_1D46B5B5CD402B3465EF80D4423AAD32" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A4AB84EC01782D65E20880D4423A8267" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_1D46B5B5CD402B3465EF80D4423AAD32" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_0DE3102E4716E32D743880D4423ABF8E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A4AB84EC01782D65E20880D4423A8267" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_0DE3102E4716E32D743880D4423ABF8E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaap_InvestmentTypeAxis_6E2F6A14F87A90CC63C380D4423A059B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_invest_InvestmentTable_49E0BD00D2959DEBB96280D4423AFDBD" xlink:to="loc_us-gaap_InvestmentTypeAxis_6E2F6A14F87A90CC63C380D4423A059B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_FEC2363FE6C8A33ADD2280D4423A8413_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_6E2F6A14F87A90CC63C380D4423A059B" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_FEC2363FE6C8A33ADD2280D4423A8413_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_FEC2363FE6C8A33ADD2280D4423A8413" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_6E2F6A14F87A90CC63C380D4423A059B" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_FEC2363FE6C8A33ADD2280D4423A8413" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShortTermInvestmentsMember" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_942F263CB2AE5C29F09880D4423ABB61" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_FEC2363FE6C8A33ADD2280D4423A8413" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_942F263CB2AE5C29F09880D4423ABB61" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherLongTermInvestmentsMember" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_57808B7F368D0D8BC5C880D4423A7DA6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_FEC2363FE6C8A33ADD2280D4423A8413" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_57808B7F368D0D8BC5C880D4423A7DA6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_00ED0F7FE58C35E55EE480D4423ABDEE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_invest_InvestmentTable_49E0BD00D2959DEBB96280D4423AFDBD" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_00ED0F7FE58C35E55EE480D4423ABDEE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_00ED0F7FE58C35E55EE480D4423ABDEE" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_00ED0F7FE58C35E55EE480D4423ABDEE" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="loc_us-gaap_CertificatesOfDepositMember_88231BCCD76E7D12DF4280D4423BAC9C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB" xlink:to="loc_us-gaap_CertificatesOfDepositMember_88231BCCD76E7D12DF4280D4423BAC9C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_6DE0B7B32EFE190D02C780D4423B525F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_6DE0B7B32EFE190D02C780D4423B525F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MutualFundMember" xlink:label="loc_us-gaap_MutualFundMember_ACF009AAA01C3988B0F580D4423B445A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB" xlink:to="loc_us-gaap_MutualFundMember_ACF009AAA01C3988B0F580D4423B445A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CorporateBondSecuritiesMember" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_2033E415A0647C79A9BE80D4423B27E7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_2033E415A0647C79A9BE80D4423B27E7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherDebtSecuritiesMember" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_2E5CD9CC265EA06699B080D4423BB5E3" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_2E5CD9CC265EA06699B080D4423BB5E3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_2072E59B91A1C1BE649480D4423BC5A3" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB" xlink:to="loc_us-gaap_CommonStockMember_2072E59B91A1C1BE649480D4423BC5A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityFundsMember" xlink:label="loc_us-gaap_EquityFundsMember_50562D2C73E041DFD36480D4423BB34E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB" xlink:to="loc_us-gaap_EquityFundsMember_50562D2C73E041DFD36480D4423BB34E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockMember" xlink:label="loc_us-gaap_PreferredStockMember_6E3A53762FA1F3AB751E80D4423BB262" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_A7D0A4ED5935B2620EB980D4423BD6BB" xlink:to="loc_us-gaap_PreferredStockMember_6E3A53762FA1F3AB751E80D4423BB262" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_A8EC322B95C8AA3F2CF580D4423B54CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A9612B18F794C2E765FE80D4423B7C37" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_A8EC322B95C8AA3F2CF580D4423B54CA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAmortizedCost" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_2B645F98DBCDB946E07080D4423B03A1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A9612B18F794C2E765FE80D4423B7C37" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_2B645F98DBCDB946E07080D4423B03A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_289DD72E4F55CD4A5E6680D4423B922C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A9612B18F794C2E765FE80D4423B7C37" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_289DD72E4F55CD4A5E6680D4423B922C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_132E179F98AABB903D1480D4423BE5A1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A9612B18F794C2E765FE80D4423B7C37" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_132E179F98AABB903D1480D4423BE5A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvestmentsFairValueDisclosure" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_127DA3E3DD206AF5906580D4423B79F9" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A9612B18F794C2E765FE80D4423B7C37" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_127DA3E3DD206AF5906580D4423B79F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvestmentsAndCash" xlink:label="loc_us-gaap_InvestmentsAndCash_AC0FB52554DB0CA31C5480D4423C619B" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A9612B18F794C2E765FE80D4423B7C37" xlink:to="loc_us-gaap_InvestmentsAndCash_AC0FB52554DB0CA31C5480D4423C619B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleOfUnrealizedLossOnInvestmentsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/SegmentReporting" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/SegmentReportingScheduleOfAutomotiveAndOtherSegmentReportingDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_1299F34602092482379E56F00EB3D558" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_1E39AFDA62016825A5B956F00EADED57" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1299F34602092482379E56F00EB3D558" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_1E39AFDA62016825A5B956F00EADED57" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_3744D66BDC4BFB1BDEA556F00EAE0E1F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_1E39AFDA62016825A5B956F00EADED57" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_3744D66BDC4BFB1BDEA556F00EAE0E1F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_ED3BD78D07B0DB63217E56F00EAEA53E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_3744D66BDC4BFB1BDEA556F00EAE0E1F" xlink:to="loc_us-gaap_SegmentDomain_ED3BD78D07B0DB63217E56F00EAEA53E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_ED3BD78D07B0DB63217E56F00EAEA53E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_3744D66BDC4BFB1BDEA556F00EAE0E1F" xlink:to="loc_us-gaap_SegmentDomain_ED3BD78D07B0DB63217E56F00EAEA53E" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_AutomotiveProductsSegmentMember" xlink:label="loc_gntx_AutomotiveProductsSegmentMember_741E5669CF45D7689F1656F00EAE2E10" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ED3BD78D07B0DB63217E56F00EAEA53E" xlink:to="loc_gntx_AutomotiveProductsSegmentMember_741E5669CF45D7689F1656F00EAE2E10" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AllOtherSegmentsMember" xlink:label="loc_us-gaap_AllOtherSegmentsMember_EECDB4249EDFE9744E8956F00EB3DB43" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ED3BD78D07B0DB63217E56F00EAEA53E" xlink:to="loc_us-gaap_AllOtherSegmentsMember_EECDB4249EDFE9744E8956F00EB3DB43" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SalesRevenueGoodsNet" xlink:label="loc_us-gaap_SalesRevenueGoodsNet_14768F90375349C4B4F656F00EB3A821" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1299F34602092482379E56F00EB3D558" xlink:to="loc_us-gaap_SalesRevenueGoodsNet_14768F90375349C4B4F656F00EB3A821" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_B86231DC0F4ABAA6C2CD56F00EB378DB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_1299F34602092482379E56F00EB3D558" xlink:to="loc_us-gaap_OperatingIncomeLoss_B86231DC0F4ABAA6C2CD56F00EB378DB" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.gentex.com/role/SegmentReportingTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlans" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_FC50677BE1426D86484E57EF39E671E7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_FC50677BE1426D86484E57EF39E671E7" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_73995130CCFAA9A86B7157EF39E68D12" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_FC50677BE1426D86484E57EF39E671E7" xlink:to="loc_us-gaap_AwardTypeAxis_73995130CCFAA9A86B7157EF39E68D12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A972446F1CEB3C1A95EA57EF39E6E5A9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_73995130CCFAA9A86B7157EF39E68D12" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A972446F1CEB3C1A95EA57EF39E6E5A9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A972446F1CEB3C1A95EA57EF39E6E5A9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_73995130CCFAA9A86B7157EF39E68D12" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A972446F1CEB3C1A95EA57EF39E6E5A9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StockCompensationPlanMember" xlink:label="loc_us-gaap_StockCompensationPlanMember_587F6D0C47776870215557EF39E66383" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A972446F1CEB3C1A95EA57EF39E6E5A9" xlink:to="loc_us-gaap_StockCompensationPlanMember_587F6D0C47776870215557EF39E66383" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_9807273189410AFAA77357EF39E65506" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_A972446F1CEB3C1A95EA57EF39E6E5A9" xlink:to="loc_us-gaap_EmployeeStockOptionMember_9807273189410AFAA77357EF39E65506" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis" xlink:label="loc_us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis_E90976D125AF8F3F96C757EF39E687B8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_FC50677BE1426D86484E57EF39E671E7" xlink:to="loc_us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis_E90976D125AF8F3F96C757EF39E687B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockOwnershipPlanESOPPlanDomain" xlink:label="loc_us-gaap_EmployeeStockOwnershipPlanESOPPlanDomain_1A8E31423E7160B19AA257EF39E69B53_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis_E90976D125AF8F3F96C757EF39E687B8" xlink:to="loc_us-gaap_EmployeeStockOwnershipPlanESOPPlanDomain_1A8E31423E7160B19AA257EF39E69B53_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockOwnershipPlanESOPPlanDomain" xlink:label="loc_us-gaap_EmployeeStockOwnershipPlanESOPPlanDomain_1A8E31423E7160B19AA257EF39E69B53" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis_E90976D125AF8F3F96C757EF39E687B8" xlink:to="loc_us-gaap_EmployeeStockOwnershipPlanESOPPlanDomain_1A8E31423E7160B19AA257EF39E69B53" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_EmployeeStockOptionPlanMember" xlink:label="loc_gntx_EmployeeStockOptionPlanMember_C52CAE991B3F0744ED9657EF39E60BF4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeStockOwnershipPlanESOPPlanDomain_1A8E31423E7160B19AA257EF39E69B53" xlink:to="loc_gntx_EmployeeStockOptionPlanMember_C52CAE991B3F0744ED9657EF39E60BF4" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_NonEmployeeDirectorStockOptionPlanMember" xlink:label="loc_gntx_NonEmployeeDirectorStockOptionPlanMember_1FD0E687130FC21281F057EF39E71748" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeStockOwnershipPlanESOPPlanDomain_1A8E31423E7160B19AA257EF39E69B53" xlink:to="loc_gntx_NonEmployeeDirectorStockOptionPlanMember_1FD0E687130FC21281F057EF39E71748" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_EmployeeStockPurchasePlanMember" xlink:label="loc_gntx_EmployeeStockPurchasePlanMember_4C5ACFDD89FBED37E9C557EF39E7C39D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeStockOwnershipPlanESOPPlanDomain_1A8E31423E7160B19AA257EF39E69B53" xlink:to="loc_gntx_EmployeeStockPurchasePlanMember_4C5ACFDD89FBED37E9C557EF39E7C39D" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_RestrictedStockPlanMember" xlink:label="loc_gntx_RestrictedStockPlanMember_1B5B6235028ECE1A5FB657EF39E75F8B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeStockOwnershipPlanESOPPlanDomain_1A8E31423E7160B19AA257EF39E69B53" xlink:to="loc_gntx_RestrictedStockPlanMember_1B5B6235028ECE1A5FB657EF39E75F8B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_8E570F7B4EC3DB16B54B57EF39E7878A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_FC50677BE1426D86484E57EF39E671E7" xlink:to="loc_us-gaap_RangeAxis_8E570F7B4EC3DB16B54B57EF39E7878A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_6D28F51711EA53FE255B57EF39E73A18_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_8E570F7B4EC3DB16B54B57EF39E7878A" xlink:to="loc_us-gaap_RangeMember_6D28F51711EA53FE255B57EF39E73A18_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_6D28F51711EA53FE255B57EF39E73A18" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_8E570F7B4EC3DB16B54B57EF39E7878A" xlink:to="loc_us-gaap_RangeMember_6D28F51711EA53FE255B57EF39E73A18" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_CF260FCC105D1126B81A57EF39E714F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_6D28F51711EA53FE255B57EF39E73A18" xlink:to="loc_us-gaap_MinimumMember_CF260FCC105D1126B81A57EF39E714F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_1C2EEBF47523B5C76B9657EF39E7E275" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_6D28F51711EA53FE255B57EF39E73A18" xlink:to="loc_us-gaap_MaximumMember_1C2EEBF47523B5C76B9657EF39E7E275" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_SharebasedCompensationArrangementbySharebasedPaymentAwardNumberofPlans" xlink:label="loc_gntx_SharebasedCompensationArrangementbySharebasedPaymentAwardNumberofPlans_AB0539021D6B6A786D9A57EF39E73A62" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_gntx_SharebasedCompensationArrangementbySharebasedPaymentAwardNumberofPlans_AB0539021D6B6A786D9A57EF39E73A62" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_1D5FBC7CDFBFC3BBA82D57EF39E79EB0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_1D5FBC7CDFBFC3BBA82D57EF39E79EB0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionCapitalizedCost" xlink:label="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionCapitalizedCost_2EA4926957437A13556657EF39E8CBD1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionCapitalizedCost_2EA4926957437A13556657EF39E8CBD1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_CD6D5803D0B19B9501D857EF39E8CDD0" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_CD6D5803D0B19B9501D857EF39E8CDD0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_19FBE066C7610AE2A15657EF39E80387" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_19FBE066C7610AE2A15657EF39E80387" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_EFB94C37CB8F0A69248057EF39E8E117" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_EFB94C37CB8F0A69248057EF39E8E117" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_FEA0AB43C9325D5A3A8357EF39E89203" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_FEA0AB43C9325D5A3A8357EF39E89203" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_F1DE7CAD6EE6DFD637CB57EF39E8EAC7" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_F1DE7CAD6EE6DFD637CB57EF39E8EAC7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_6610747A8B54FAEAD75557EF39E81961" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_6610747A8B54FAEAD75557EF39E81961" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP" xlink:label="loc_us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP_77725793AEC9D801CAC757EF39E8B694" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP_77725793AEC9D801CAC757EF39E8B694" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_23C40393B77293A3580157EF39E8E384" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_23C40393B77293A3580157EF39E8E384" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockOwnershipPlanESOPNumberOfAllocatedShares" xlink:label="loc_us-gaap_EmployeeStockOwnershipPlanESOPNumberOfAllocatedShares_072AF71F2D5AC2D3772B57EF39E800EA" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_EmployeeStockOwnershipPlanESOPNumberOfAllocatedShares_072AF71F2D5AC2D3772B57EF39E800EA" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense_91DC89DAC940C2D0514157EF39E8009B" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense_91DC89DAC940C2D0514157EF39E8009B" xlink:type="arc" />
    <link:loc xlink:href="gntx-20170630.xsd#gntx_ShareBasedCompensationRestrictedPeriod" xlink:label="loc_gntx_ShareBasedCompensationRestrictedPeriod_43A5FA714CB49B8C2E3157EF39E8A2F2" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_gntx_ShareBasedCompensationRestrictedPeriod_43A5FA714CB49B8C2E3157EF39E8A2F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredCompensationEquity" xlink:label="loc_us-gaap_DeferredCompensationEquity_68DD75DCC79D1BBB110457EF39E9275A" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_DeferredCompensationEquity_68DD75DCC79D1BBB110457EF39E9275A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedStockExpense" xlink:label="loc_us-gaap_RestrictedStockExpense_FA867C5BB95C068F95B657EF39E936DA" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_848F08FE03C125777B3157EF39E7FC33" xlink:to="loc_us-gaap_RestrictedStockExpense_FA867C5BB95C068F95B657EF39E936DA" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansWeightedAverageAssumptionsForEsopDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedBalanceSheets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsOfCashFlows" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsOfComprehensiveIncome" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsOfIncome" xlink:type="extended" />
</link:linkbase>
