This book constitutes the refereed proceedings of the 17th International Semantic Web Conference, ESWC 2020, held in Heraklion, Crete, Greece.* The 39 revised full papers presented were carefully reviewed and selected from 166 submissions. The papers were submitted to three tracks: the research track, the resource track and the in-use track. These tracks showcase research and development activities, services and applications, and innovative research outcomes making their way into industry. The research track caters for both long standing and emerging research topics in the form of the following subtracks: ontologies and reasoning; natural language processing and information retrieval; semantic data management and data infrastructures; social and human aspects of the Semantic Web; machine learning; distribution and decentralization; science of science; security, privacy, licensing and trust; knowledge graphs; and integration, services and APIs. *The conference was held virtually due to the COVID-19 pandemic. Chapter 'Piveau: A Large-scale Oopen Data Management Platform based on Semantic Web Technologies' is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.