The Edersee, also known as the Ederstausee, is an 11.8 km2 (4.6 sq mi) reservoir in Waldeck-Frankenberg, Hesse, Germany holding back an estimated 199.3 million m3 (7.04 billion cu ft).

It is on the chief western tributary of the Fulda, the Eder, behind the 48 m-high (157 ft) Edersee Dam near the town of Waldeck in the Waldeck-Frankenberg district of North Hesse.

The dam also protects downstream residents from small and medium floods, generates electrical energy and the lake is used for sports and leisure.

This fairly brief central portion of the Eder has its dam near Hemfurth-Edersee, about 35 km (22 mi) south-west of Kassel, linked by a winding road.

Beyond an intermittent band of tree-lined fields to the south associated with two shoreside villages is the "Ederhöhen", very high, often steep, wooded foothills to the Kellerwald mountain range – together they form a protected upland forest roughly congruent with the Nationalpark Kellerwald-Edersee.This is the largest lake in Hesse.