Prášilské jezero, Glacial lake in Prášily, Czech Republic.

Prášilské jezero is a glacial cirque lake in the Bohemian Forest (Šumava), Czech Republic, at 1,080 m altitude and 3.7 ha in area, up to 15 m deep. It lies between the steep slopes of Poledník (1,315 m) and Skalka (1,237 m), about 5 km from Prášily and 2 km from the German border. The lake is held back by a 9 m wall of granite boulders and two older moraine ridges.

The lake was formed during the last Ice Age, when glaciers carved a hollow into the rock and left behind a deep basin. After the ice retreated, the basin filled with water and has remained ever since.

Prášilské jezero sits within the core protection zone of Šumava National Park, where nature is largely left to follow its own course. Visitors can observe the still water from the shore and notice how the surrounding forest grows dense and undisturbed.

The lake is reached from Prášily village by following a marked trail through forested slopes. The path suits most walkers but can be wet and uneven in places, so sturdy footwear is a good idea.

In 2019 the ciliate lahvenka velká (a trumpet-shaped protozoan) was recorded in the lake, the first find of this species in the Czech Republic. The lake drains via Jezerní potok into the Křemelná, then the Otava, Vltava and Labe. A stone monument on the granite dam recalls student O. Kareis, who drowned here in 1927.