The Eder is a river in Germany (ca. 135 km long). It rises from the Ederkopf mountain in the mountains of western North Rhine-Westphalia near the springs of the Lahn and Sieg rivers, but flows east and north and into the Fulda river which at its confluence with the Werra in Hannoversch Münden creates the Weser river which flows into the North Sea north of Bremen. Towns along its course include Battenberg, Frankenberg , Waldeck and Fritzlar.

A dam (47 m high, 400 m long) completed in 1914 near the small town of Waldeck created the large reservoir Edersee, which is 27 km long and used to generate hydro-electricity and to regulate water levels for shipping on the Weser river. The dam was destroyed on May 17, 1943, during the same night as the near-by Möhne reservoir dam, by British Avro Lancaster bombers of No. 617 Squadron RAF equipped with special Barnes Wallis bouncing bombs for the attack, causing enormous destruction and loss of life downstream (the great majority of drowning victims were Ukrainian POWs in a labor camp just below the dam). The dam was rebuilt, and the lake today is a major summertime recreation facility, particularly popular with Dutch campers.