Lac de Kruth-Wildenstein, Artificial reservoir in the Vosges mountains, France.

The Lac de Kruth-Wildenstein stretches across 81 hectares at an elevation of 545 meters, surrounded by dense forests and reaching a maximum depth of 35 meters in the Vosges mountain range.

Construction of this artificial lake began in 1959 following devastating floods in 1947, with the project completed in 1963 to regulate the Thur river and prevent future flood damage in the valley.

The lake's name links it to Wildenstein even though 95% of its surface lies in Kruth and 5% in Fellering. Above the southern shore rises the 666 m Schlossberg with the ruined castle of Wildenstein. Since 2004 the Arbre Aventure park has added forest rope courses, a zip line and a via ferrata beside the water.

The lake lies between Wildenstein to the north and Kruth to the south, with the Schlossberg and its castle ruin closing the southern end. The Kruth railway station, terminus of the Lutterbach–Kruth line, is about three kilometres away. A campsite stands near the lake, and the Arbre Aventure park, created in 2004, offers forest courses, a zip line and a via ferrata.

The dam is a gravity structure without a clay core, a technique common in Germany, with a watertight upstream face of bituminous concrete laid in four successive layers. It is owned by the department. Because the Thur's flow is weak at this point, no hydroelectric plant was built. During the flood of 4–5 January 2018 it held back over 1.5 million m³ and cut the Thur's peak discharge by 24 m³/s, about 25%.