Hildesheim cathedral library, Cathedral library in Hildesheim, Germany.

Hildesheim Cathedral Library is a diocesan research library holding more than 120,000 volumes, among them medieval manuscripts and rare incunabula. Since 1996 it has occupied a postmodern new building at Domhof 30, designed by Reinhard and Andreas Fritsch of Oldenburg, on the north side of the Great Cathedral Square. It offers reading rooms and public lending.

Founded with the diocese in 815, the library has existed without interruption since then, making it the oldest library in northern Germany. Its original cathedral-school holdings were repeatedly reduced by fires; the collection grew through secularised monastery libraries, the former Jesuit college, and private collections such as the Beverina, acquired in 1681 from pastor Martin Bever of Groß Förste. In 1908 the library of the Basilica of St. Godehard was added. Holdings were moved out in time to escape the air raids of World War II.

The collection holds books connected to the cathedral chapter since the diocese was established, representing centuries of religious and academic traditions in the region.

The reading room offers various work stations, specialized tables for manuscript study, and spaces for focused research or smaller groups. Visitors should inquire in advance about which areas are accessible and how to request materials.

The Albani Psalter, made around 1125, is the library's best-known manuscript. A lesser-known piece is the Codex Rotundus, a circular late-medieval book of hours that belonged to Adolf of Cleves (1425–1492). A Missale lost in the unexplained losses of the 1970s has never been recovered.