The Königssee is a natural lake in the extreme southeast Berchtesgadener Land district of the German state of Bavaria, near the border with Austria. 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 2700 m (8900 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 torn down 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.
The literal translation of the name, Königssee, appears to be "king's lake"; however while German: König does indeed mean "king", there had been no Bavarian kings since the days of Louis the German until Elector Maximilian I Joseph assumed the royal title in 1806. Therefore the name more probably stems from the first name Kuno of local nobles, who appear in several historical sources referring to the donation of the Berchtesgaden Provostry in the twelfth century; the lake was formerly called Kunigsee.