Lake Lauerz (German: Lauerzersee, old spelling: Lowerzer See) is a lake in the Canton of Schwyz , Switzerland .

Its water area varies between 310 ha (766.0 acres) and 360 ha (889.6 acres) (depending on water level), a maximum depth of 14 m (45.9 ft), and a water level elevation above sea level of 447 m (1,466.5 ft).

The lake's water area is divided between the municipalities of Lauerz, Schwyz and Steinen. There are two small islands in the lake, Schwanau and Roggenburg, both of which are in the municipality of Lauerz. The villages of Lauerz, on the southern side of the lake and in its eponymous municipality, and Seewen, at the eastern end of the lake in the municipality of Schwyz, lie on or close to the shore of the lake.

The lake's principal inflow is the Steiner Aa, which flows into the north shore of the lake having passed through the village of Steinen, along with a number of smaller streams.