| | | | | | | | | | | | | | | | | | | | | |
<?xml version="1.0" encoding="windows-1252"?> |
<!-- XBRL Document Created with Wdesk from Workiva --> |
<!-- Copyright 2021 Workiva --> |
<!-- r:eae1b278-e8b0-4b01-ac74-3ef2785ecc6b,g:74839309-de37-4b45-ba3a-2e728b0a4697 --> |
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"> |
| <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/> |
| <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/> |
| <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/> |
| <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/> |
| <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/> |
| <link:roleRef roleURI="http://www.knight-swiftinc.com/role/DocumentandEntityInformationDocument" xlink:type="simple" xlink:href="knx-20210419.xsd#DocumentandEntityInformationDocument"/> |
| <link:definitionLink xlink:role="http://www.knight-swiftinc.com/role/DocumentandEntityInformationDocument" xlink:type="extended" id="i9266c6174a4e43e3af17f0dd696cbeec_DocumentandEntityInformationDocument"/> |
| </link:linkbase> |