Burg Rappelstein, Medieval castle ruins in Nordenau, Schmallenberg, Germany.

Burg Rappelstein is a castle ruin situated on a rocky outcrop above the Nesselbach valley in Schmallenberg. The preserved tower structure provides views over the forested valley and surrounding hills.

The lords of Grafschaft built the castle around 1200 on the Rappelstein rock, shifting their seat from Wilzenberg. In 1298 the brothers Kraft and Widekind sold it to Count Otto of Waldeck and received it back as a fief. From 1343 Cologne and Waldeck fought over it until a 1364 agreement made it joint property. After 1471 it decayed.

The name Rappelstein comes from the rock in Nordenau's centre where the castle stands. The lords of Grafschaft were hereditary protectors (Vögte) of Grafschaft Abbey, and after building the castle around 1200 they moved their seat here while keeping authority over the abbey's lands. A 25 cm bronze bowl inscribed SUR ERBIA, found in the ruins, has been in the LWL museum in Münster since 1927.

The ruin stands on the Rappelstein rock in the centre of Nordenau, so it is reached on foot from the village rather than by a country trail. The Bergfried was partly rebuilt in 1967/68 and now serves as a viewing platform over Nordenau, the Nesselbach valley and the surrounding Sauerland hills.

Scientific studies suggest that parts of the tower structure are older than historians originally believed. This finding makes the ruin one of the oldest surviving structures in the surrounding region.