The
Bishopric of Brandenburg was a
Roman Catholic diocese established by
Otto the Great in 948, including the territory between the
Elbe on the west, the
Oder on the east, and the
Schwarze Elster on the south, and taking in the
Uckermark to the north. Its seat was
Brandenburg upon Havel. It was a state of the
Holy Roman Empire for some time, probably starting at 1161/1165, but never managed to gain control over a significant territory, being overshadowed by the
Margraviate of Brandenburg, which was originally seated in the same city. Chapter and cathedral, surrounded by further ecclesiastical institutions, were located on Dominsel (cathedral island), which formed a
prince-episcopal immunity district, distinct from the city of Brandenburg. Only in 1929 the - meanwhile former - immunity district was incorporated into the city itself.