Fehmarn is an island in the Baltic Sea, off the eastern coast of Germany's northernmost state of Schleswig-Holstein. It is Germany's third-largest island, after Rügen and Usedom. Fehmarn is separated from the German peninsula of Wagria in Holstein by the Fehmarn Sound, and from the southern Danish island of Lolland by the Fehmarn Belt. It is connected to the Holsatian mainland by the Fehmarn Sound Bridge. The island belongs to the district of Ostholstein. The closest larger towns on the mainland are Heiligenhafen and Oldenburg in Holstein. Right opposite Fehmarn, on the tip of the Wagrian Peninsula, is Großenbrode.

Schleswig-Holstein is the northernmost of the 16 states of Germany, comprising most of the historical Duchy of Holstein and the southern part of the former Duchy of Schleswig. Its capital city is Kiel; other notable cities are Lübeck and Flensburg. It covers an area of 15,763 km2 (6,086 sq mi), making it the 5th smallest German federal state by area.