UK Archival Thesaurus (UKAT) is a subject thesaurus created for the archive sector in the United Kingdom. It is a controlled vocabulary that archives can use when indexing their collections and catalogues. It is intended to improve access to archives by subject, ensure that users of archives can carry out effective subject searches of archives across the UK, and promote the involvement in archives by groups which are under-represented among archive users by providing subject terms which reflect their histories and experiences. UKAT is based on the structure of the UNESCO Thesaurus, and covers education, science, culture, social/human sciences, information, communication, politics, law and economics. UNESCO was used as the basis for UKAT because a number of archives and archive projects, including The Archives Hub, had adopted it for indexing purposes. However, UNESCO sometimes lacks the depth of detailed terminology required by UK archives. UKAT therefore incorporates terms that UK repositories and projects have contributed, or have been sourced from other schemes such as Library of Congress Subject Headings and the British Education Thesaurus. Particular emphasis has been given to incorporating terms reflecting the histories and experiences of groups that are under-represented among archive users. This aims to encourage participation in archival heritage, in line with national priorities for the sector.