Edersee, Artificial lake in Waldeck-Frankenberg, Germany.

Edersee is a reservoir in Waldeck-Frankenberg, northern Hesse, stretching nearly thirty kilometers between forested slopes. The reservoir sits within the Kellerwald-Edersee Nature Park and fills a long, narrow valley with numerous bays and side arms.

The dam was built between 1908 and 1914, requiring three villages to be moved to higher ground. In May 1943, British bombers damaged the dam wall severely, causing floods in the valley below.

The lake's name comes from the Eder, the Fulda tributary that feeds it from the Rothaargebirge. When the water drops, the old village site of Asel reappears, marked as a "Dorfstelle" with its church foundations, and the sunken bridge of Bringhausen becomes visible. The reservoir is used for sailing, fishing and boating.

The dam wall near Hemfurth-Edersee and the viewpoints above the shore give the widest views over the water and the wooded slopes. Because the reservoir regulates the Weser and the Mittellandkanal, its level can fall sharply in dry summers; in August 2025 it held only about 38 million m³, roughly 19 percent of capacity.

When water levels drop, the foundations of the old villages reappear, including bridges and house foundations from before the dam was built. Visitors can then walk along the former village streets and explore the ruins of Asel and Berich settlements.