The Schluchsee is a reservoir lake in the district of Breisgau-Hochschwarzwald, southeast of the Titisee in the Black Forest near Freiburg im Breisgau, Germany.
The Schluchsee, with its height of 930 metres (3,050 ft) above sea level, is the highest reservoir in Germany and also the largest lake in the Black Forest. By contrast the Hornberg Basin (Hornbergbecken), is 1,048 metres above sea level, but is the upper basin of a pumped storage hydropower station, rather than a reservoir.
The water of the reservoir is relatively cool even in summer because of its high elevation.
The best-known settlements around the Schluchsee are on its northern shores and include the eponymous town of Schluchsee and the hamlets of Seebrugg by the dam itself and Aha. The Three Lakes Railway, an extension of the Höllentalbahn, runs from Titisee station along the northern shore to the terminus at Seebrugg.