The two-volume set LNCS 11136 and 11137 constitutes the refereed proceedings of the 17th International Semantic Web Conference, ISWC 2018, held in Monterey, USA, in October 2018. The ISWC conference is the premier international forum for the Semantic Web / Linked Data Community. The total of 62 full papers included in this volume was selected from 250 submissions. The conference is organized in three tracks: for the Research Track 39 full papers were selected from 164 submissions. The Resource Track contains 17 full papers, selected from 55 submissions; and the In-Use track features 6 full papers which were selected from 31 submissions to this track.Paper 'The SPAR Ontologies' is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.