This book constitutes the thoroughly refereed proceedings of the 15th International Conference on Metadata and Semantic Research, MTSR 2021, held as a virtual event in November-December 2021. The 27 full and 7 short papers presented were carefully reviewed and selected from 92 submissions. The papers are organized in the following topical sections: metadata, linked data, semantics and ontologies - general session, and track on agriculture, food and environment; track on open repositories, research information systems and data infrastructures; track on knowledge IT artifacts (KITA) and decentralized applications, blockchains and P2P systems, and general session; track on digital humanities and digital curation, and general session; track on digital libraries, information retrieval, big, linked, social and open data; track on european and national projects, and general session; track on cultural collections and applications, and general session.

This book constitutes the thoroughly refereed proceedings of the 14th International Conference on Metadata and Semantic Research, MTSR 2020, held in Madrid, Spain, in December 2020. Due to the COVID-19 pandemic the conference was held online. The 24 full and 13 short papers presented were carefully reviewed and selected from 82 submissions. The papers are organized in the following tracks: metadata, linked data, semantics and ontologies; metadata and semantics for digital libraries, information retrieval, big, linked, social and open data; metadata and semantics for agriculture, food, and environment, AgroSEM 2020; metadata and semantics for open repositories, research information systems and data infrastructures; digital humanities and digital curation, DHC 2020; metadata and semantics for cultural collections and applications; european and national projects; knowledge IT artifacts (KITA) in professional communities and aggregations, KITA 2020.