Čertovo Jezero (Devil's Lake) is one of five morainic lakes in the Czech part of the Šumava mountains (Bohemian Forest) and it is the second largest, after the near Černé Jezero (Black Lake).
The lake lies on the south-western slope of Jezerní Hora (Lake Mount - 1,343 m), 1,030 m a.s.l.

The lake was dug out by the movement of glaciers in the Pleistocene. It is about 10 ha large and its maximal depth is about 37 m. Two brooks take water into Černé Jezero and the Jezerní Potok (Lake Stream) runs out of the lake.
The lake belongs to the river basin of the Danube river, which empties into the Black Sea. Černé Jezero, which lies only about 1.5 km far, is in the basin of the Vltava river, which takes water into the Elbe river and then into the North Sea) and the main European watershed leads between both lakes.
The nature reserve Černé a Čertovo Jezero (Black and Devil's Lakes) was established to protect both the lakes.

The yellow marked path leads from Špičácké Sedlo (about 3 km north of the town Železná Ruda near the road to the town Nýrsko) to the lake (about 2.5 km). The red marked trail then continues to Černé Jezero over the European watershed and then it runs through the nature reserve Bílá Strž (White Flume) with 14 m high waterfall.