Totesee (Germanized: Totensee) is a small natural lake (18 ha or 44 acres) at the Grimsel Pass in Switzerland.

The lake lies immediately to the south of the natural watershed and cantonal boundary at the pass.

It is therefore in the canton of Valais, and it would naturally drain into the river Rhône in the valley below.

However a dam has been constructed to enable its use as a reservoir, increasing its size and raising its level by 16 metres (52 ft).

[1][2] In November 2006, the lake's entire trout population died, possibly due to algae.