The Edersee is a large reservoir created by the construction, from 1908 to 1914, of a dam across the Eder river, near the small town of Waldeck in northern Hesse, Germany, to generate hydropower and regulate water levels for shipping on the Weser river.  

The dam was destroyed by special bouncing bombs dropped by British Lancaster bombers during the night of May 16/17, 1943, creating massive destruction and loss of life downstream (see Operation Chastise), including the drowning death of 749 Ukrainian POWs in a labor camp just below the dam. Through the breach in the dam, 70 meters wide and 22 meters deep, some 8,000 m³ of water per second emptied in the narrow valley below, a total of about 160 million m³. A flood wave of 6-8 meter height roared through the river valley as far as 30 km downstream, before it diminished in the widening floodplains of the lower Eder, the Fulda and the Weser.

The dam was rebuilt within months by forced labor (see Organisation Todt), and the lake today is a major summertime recreational facility. It has a capacity of 199.3 million m³, which makes it the third largest reservoir in Germany. It is a very popular summertime recreation area.

At low water, in late summers of dry years, the remnants of three villages (Asel, Bringhausen, and Berich), along with a bridge across the original river bed, that were submerged when the lake was filled in 1914, can be seen, and descendants of people buried in the now submerged cemetaries go to visit the graves of their ancestors.