The Martinus Library is the academic diocesan library of the Diocese of Mainz and is located at the Episcopal Seminary of St. Boniface. With a history spanning over 350 years—the Martinus Library was founded in 1662 by Archbishop and Elector Johann Philipp von Schönborn—it is the oldest library in Mainz that has existed continuously to this day. Since 1968, it has been located in the Arnsburger Hof (Grebenstraße 8) in Mainz’s Old Town. Since 2000, it has been named after Martin of Tours, the patron saint of Mainz Cathedral and the diocese.

The Martinus Library holds an extensive collection of over 300,000 volumes in theology and the humanities, 140 current journals, and numerous manuscripts as well as historical prints covering all fields of knowledge. The library is open to the public, serves all interested parties, and provides literature and information for the diocese and the academic community. Use of the library and its collections is free of charge.

The Martinus Library’s research and collection focus stems from its role as a diocesan library and from its historically accumulated holdings. It encompasses the entire field of Catholic theology. Of particular importance here is the history of the Church and piety, especially in the Mainz region. In addition, the library offers literature in the fields of philosophy, source editions, religious studies, history with a focus on the Mainz region, manuscript studies and the history of printing, German studies (Old High German literature and the Goethe era), and classical philology. The Martinus Library assumes the legal obligation to provide deposit copies for the diocesan publications of the Diocese of Mainz and all parish offices and pastoral centers within the diocese, and permanently archives these holdings.

All holdings of the Martinus Library dating from 1970 onward are recorded in the online catalog and can be searched. Through the ongoing cataloging of older holdings, some of these are also included in the digital catalog. For books that cannot be found via the online catalog search, an alphabetical card catalog is available on site.