Recent standardization on the Web of Things and (Social) Linked Data unlocks new practical use cases and new opportunities for research on Web-based multi-agent systems. While existing research on multi-agent systems can contribute to engineering adaptive and flexible Web-based systems, increased deployment of systems following the recent standards can bring new insight into engineering large-scale and open multi-agent systems. These developments motivate the need for a broader perspective that can only be achieved through a concerted effort of the research communities on Web Architecture and Web of Things, Semantic Web and Linked Data, and Autonomous Agents and Multi-Agent Systems. Thus, the main objective of the Dagstuhl Seminar 23081 on Agents on the Web was to investigate these new research opportunities, to support the transfer of knowledge and results across the different communities, and to create a network of leading scholars and practitioners around these topics. This report documents the seminar’s program and outcomes. To continue the joint work after the seminar, the seminar participants created the W3C Autonomous Agents on the Web (WebAgents) Community Group.