Sieseby in Schwansen
Bilingual map of Schwansen

Schwansen (Danish: Svans or Svansø, meaning "swan lake") is a peninsula in Schleswig-Holstein, Germany, protruding into the Baltic Sea. It is located between the Eckernförde Bay in the south and the Schlei inlet in the north.

The Danish dialect South Jutlandic was still spoken in Schwansen around 1780 (the last time in the villages near the Schlei). Denmark lost Schwansen during the Second Schleswig War in 1864.

Schwansen is the name of the former Amt ("collective municipality") Schwansen, which covered most of the peninsula. The seat of the Amt was in Damp.

Coordinates: 54°34′N 9°54′E / 54.567°N 9.900°E / 54.567; 9.900