This book constitutes the refereed proceedings of the 3rd European Semantic Web Conference, ESWC 2006, held in Budva, Montenegro in June 2006.

The 48 revised full papers presented together with abstracts of 3 invited talks were carefully reviewed and selected from a total of 181 submitted papers. The papers are organized in topical sections on ontology alignment, engineering, evaluation, evolution and learning, rules and reasoning, searching and quering, semantic annotation, semantic web minig and personalisation, semantic web services, semantic wiki and blogging, as well as trus and policies.