The Diocese of Osnabrück is a Latin Church ecclesiastical territory or diocese of the Catholic church in Germany. The diocese was originally founded circa 800. It should not be confused with the smaller Prince-Bishopric of Osnabrück–an ecclesiastical principality of the Holy Roman Empire until 1803–over which the bishop, as prince-bishop, exercised both temporal and spiritual authority.

Osnabrück is a city in Lower Saxony in western Germany. It is situated on the river Hase in a valley penned between the Wiehen Hills and the northern tip of the Teutoburg Forest. With a population of 168,145 Osnabrück is one of the four largest cities in Lower Saxony. The city is the centrepoint of the Osnabrück Land region as well as the District of Osnabrück.