Traunsee is a lake in the Salzkammergut area in Austria. It is about 12 kilometres (7.5 mi) long. The lake is 3 kilometres (1.9 mi) wide and 191 metres (627 ft) deep. This depth makes it the deepest lake in Austria. It also is the second largest lake in Upper Austria.
At the north end of the lake is Gmunden, the capital of the Gmunden district . At the south end of the lake is Ebensee. The other two towns around the lake are Altmünster and Traunkirchen. At the east side of the lake is the mountain Traunstein. It is 1,619 metres (5,312 ft) high.