The medieval university at Oxford was one of the most prestigious venues in Europe for the circulation of scholars and books. In complicated networks of acquisition and exchange, books were bought, borrowed, copied, and bequeathed. Colleges came to own collections of books for the use of their fellows and built library-rooms to house their books securely. Some colleges - notably All Souls, Merton, and New College - still own large remnants of their medieval collections. This volume collects for the first time all the medieval documents that refer to library holdings in both the medieval university and its colleges, documents as varied as borrowing registers, inventories, and formal catalogues of various dates and degrees of sophistication. It takes the libraries through the critical years of the Reformation, including books from the first generations of print. Also included is a substantial biographical section on individuals who gave or bequeathed books to Oxford libraries.