The Königssee is a natural lake in the extreme southeast Berchtesgadener Land district of the German state of Bavaria, near the Austrian border. Most of the lake is within the Berchtesgaden National Park.

Situated within the Berchtesgaden Alps in the municipality of Schönau am Königsee, just south of Berchtesgaden and the Austrian city of Salzburg, the Königssee is Germany's third deepest lake. Located at a Jurassic rift, it was formed by glaciers during the last ice age. It stretches about 7.7 km (4.8 mi) in the north-south direction and is about 1.7 km (1.1 mi) across at its widest point. Except at its outlet, the Königsseer Ache at the village of Königssee, the lake similar to a fjord is surrounded by steeply rising flanks of mountains up to 2,700 m (8,900 ft), including the Watzmann massif in the west. The railway Königsseebahn served the lake from 1909 until 1965. Its last tracks were dismantled during 1971, and the station in Berchtesgaden was demolished in 2012. The only remaining element of the railway is the Königsee station (now a restaurant). The track route is mostly used as a walking path.