This two-volume set constitutes the proceedings of the 24th International Semantic Web Conference, ISWC 2025, held in Nara, Japan, during November 2–6, 2025.The 60 full papers included in these volumes were carefully reviewed and selected from 277 submissions. These papers address theoretical, analytical, and empirical aspects of the Semantic Web; promote the sharing of resources that support, enable, or utilize semantic web research; and describe applied research as well as software tools, systems, or architectures that benefit from the use of Semantic Web and Knowledge Graph technologies.Chapter "COTTAS: Columnar Triple Table Storage for Efficient and Compressed RDF Management" is licensed under the terms of the Creative Commons AttributionNonCommercial-NoDerivatives 4.0 International License via Springerlink.