Berglsteiner See, Natural monument lake in Breitenbach am Inn, Austria.

Berglsteiner See is a 2.36-hectare lake in the municipality of Breitenbach am Inn, in a hollow on the south slope of the Voldöppberg at 713 m. It lies in the Brandenberg Alps and reaches a maximum depth of only two metres. Its shore holds a restaurant, and access is permitted only by bicycle.

Berglsteiner See was declared a natural monument (Naturdenkmal) in 1928, giving the 2.36-hectare lake in the municipality of Breitenbach am Inn protected status. The designation is recorded in the Tyrolean list of natural monuments.

The lake lies in a hollow on the southern slope of the Voldöppberg, a 1,509 m peak of the Brandenberg Alps, and is used as a bathing lake; a guesthouse stands on its shore. Access is permitted only by bicycle, so bathers and walkers arrive on quiet paths.

Access to Berglsteiner See is permitted only by bicycle; motor vehicles may not drive to the shore. The lake lies at 713 m in a hollow on the south slope of the Voldöppberg, and a guest house stands by the water, open as of October 2021.

The lake is only two metres deep at its deepest point, despite covering 2.36 hectares. Access is permitted only by bicycle, so visitors arriving by car must leave the vehicle behind and cycle the final stretch to the shore.