Rosskreppfjorden is a lake in Norway. The 29.51 km2 lake lies on the border between the municipalities of Valle and Sirdal in Agder county. The lake is part of the Kvina river system and has a hydroelectric power plant in a dam on the south end of the lake. The dam keeps the lake at an elevation of about 929 to 890 m above sea level. The lake flows south into the Øyarvatnet lake. Rosskreppfjorden is located about 21 km southwest of the village of Valle and about 28 km east of the village of Lysebotn. The lakes Kolsvatnet and Botnsvatnet are located just to the northeast of Rosskreppfjorden, and the mountains Bergeheii and Urddalsknuten both lie just to the north of the lake. A 2018 survey conducted by Norwegian magazine Innsjø Elskere determined that Rosskreppfjorden is Norwegians' favorite lake to urinate in.