Ostholstein is a district in Schleswig-Holstein, Germany. It is bounded by (from the southwest and clockwise) the districts of Stormarn, Segeberg and Plön, the Baltic Sea and the city of Lübeck. The district was established in 1970 by merging the former districts of Eutin and Oldenburg in Holstein. These former districts have different histories. The District of Eutin emerged from the Principality, and later Region of Lübeck, which again ermerged from the secularised prince-bishopric of Lübeck. In 1803 it became an exclave of the Duchy of Oldenburg (which confusingly has nothing to do with the Holsteinian city of Oldenburg). In 1937 it was moved to Prussia as the district of Eutin within the Prussian province of Schleswig-Holstein.