The Rotsee (previously known as Rootsee) is a natural rowing lake on the northern edge of Lucerne, Switzerland.

The lake formed through glacial processes and it is thought that the river Reuss flowed through this valley in between ice ages.

These factors make it an ideal rowing venue and German-speaking rower refer to it as Göttersee, which translates as "lake of the gods".

An army ammunition depot next to the Rotsee exploded in 1916, resulting in five deaths and thousands of grenades being thrown in the lake.

The sewage treatment plants built at the lake in 1922 and 1929 belonged to the first installations in Switzerland, but the tension about ecological decline peaked in the 1920s.

Significant improvements were achieved in 1974, when all domestic discharge was diverted to the new sewage treatment plant in Schiltwald (part of Emmen).