The Wisper is a 29.715-kilometre-long (18.464 mi) river in Hesse, Germany, right tributary of the Rhine. Its source is in the western Taunus, Rheingau-Taunus-Kreis district, near a small village named Wisper (municipality Heidenrod). It flows southwest through a densely forested valley with some medieval castle ruins surrounded by a popular hiking area. A man-made lake, the Wispersee, is stocked with trout and is a popular fishing destination.