Lake Starnberg , or Starnberger See [ˈʃtaʁnbɛʁɡɐ ˌzeː] ) — called Lake Würm or Würmsee ([ˈvʏʁmˌzeː] ) until 1962 — is Germany's fifth-largest lake by area, however, because of its great depth, it is the second-largest body of fresh water. It and its surroundings lie in three different Bavarian districts, or Landkreise. The lake is property of the state and accordingly managed by the Bavarian Administration of State-Owned Palaces, Gardens and Lakes.

Located in southern Bavaria 25 kilometres (16 mi) southwest of Munich, Lake Starnberg is a popular recreation area for the city and, since 1976, one of the wetlands of international importance protected by the Ramsar Convention. The small town of Berg is famous as the site where King Ludwig II of Bavaria was found dead in the lake in 1886. Because of its associations with the Wittelsbach royal family, the lake is also known as Fürstensee (Prince's Lake).