Verbrüderungsbuch (codex of fraternisation) is the German name for registers from monasteries in the Middle Ages. They contained lists with the names of sponsors and benefactors, as well as persons in close spiritual contact with a monastery, so that they were actively remembered in the prayers of the monks. In many cases these books were established as early as the 8th century and continued up to the 13th century. So-called Jahrtagsbücher (year books) are in many ways their successors.
Verbrüderungsbücher are a rich source for prosopography and historical linguistics of the early Middle Ages.