This study focuses on the early modern history of the monastic library of the Order of St Augustine at St Thomas in Prague. On the basis of archival sources (monastic chronicles, the catalogue of the members of the Order) and research into provenances in extant collections, this paper primarily aims to map the development of the Augustinian library in the 16th and 17th centuries. Provenance research has discovered that the monastic library was mainly used for monastic studies and for preaching and pastoral activities of the Augustinians. The research into book provenances has revealed numerous personal ties between the Lesser Town Augustinians and people at the court of Rudolph II. The results of the archival and provenance research have not confirmed the hypothesis of the complete looting of the library at the end of the Thirty Years’ War, but neither have they clearly proved the true extent of the losses suffered by the library. The research has shown the primary role of the library within the Order of St Augustine in the Czech lands and has indicated the position of the library in a broader social and cultural context., Veronika Sladká., and Obsahuje bibliografické odkazy