Lake Lungern (German: Lungerersee, also spelled Lungernsee or Lungerensee) is a natural lake in Obwalden, Switzerland which is named after the town Lungern on its shore. The lake is drained by the Sarner Aa river, which flows through the Sarnersee and into Lake Lucerne.

The lake was originally much larger, and covered a large part of the valley it is situated in. Starting in 1836, its level was lowered by 36 metres (118 ft) through an artificial drainage tunnel with a length of 380 metres (1,250 ft). It is used as a reservoir.

• List of lakes of Switzerland

• Edy von Wyl: Lungernsee in German, French and Italian in the online Historical Dictionary of Switzerland.
• Media related to Lungerersee at Wikimedia Commons