Affolderner See, Reservoir in Edertal, Hesse, Germany

Affolderner See is a 1.65 km² reservoir on the Eder, about 2.5 km downstream of the Edertalsperre between Hemfurth and Affoldern. It has a maximum storage volume of 7.6 million m³ and lies at 204.4 m above sea level. A crescent-shaped dam about 1.5 km long separates the older basin from the newer northern extension.

The first reservoir, built in 1929 with a small weir, held 0.32 million m³. In 1972 it was extended west and a northern basin added, raising capacity to 5.4 million m³; a crescent-shaped dam about 1.5 km long was left as an island between old and new water. A new weir with the Affoldern run-of-river power plant followed in 1998, bringing the maximum to 7.6 million m³.

The lake is named after Affoldern, the village at its southwestern edge. Its northern basin is designated as a fishing water, while the southern part, including the crescent-shaped dam island in the middle, is closed to people. The Eder-Draisine runs on the former E.ON industrial railway between Affoldern and Hemfurth.

The southern part of the lake, including the crescent-shaped dam island in the middle, is closed to visitors as a nature reserve; the northern basin is open for fishing. The Peterskopfbahn cable car runs up to the upper reservoirs of the Waldeck pumped-storage plants. A draisine rail cart operates on the former E.ON line between Affoldern and Hemfurth.

Just north of the dam, near the edge of Affoldern on the L 3086 road from the Edersee dam, stands Das Tolle Haus Am Edersee: the building and everything inside it is mounted upside down. It is easy to drive past on the way to the lake.