Tannensee is a reservoir in Obwalden, Switzerland.

In 1958, Tannenbach and few other creeks were dammed with an earth-fill dam.

The reservoir has a volume of 3.8 mio m³ and its surface area is 33 ha (82 acres).

The reservoir is used to generate electricity at Kraftwerk Hugschwendi in Kerns.

This article related to a lake in Obwalden is a stub.