Schadeck Castle, Medieval castle in Schadeck, Runkel, Germany.

Schadeck Castle is a castle in the village of Schadeck, in the German state of Hesse, set on a rocky spur above the Lahn River. The main building is rectangular, rises three and a half stories, and has a staircase tower attached to its western side.

Henry of Westerburg built Schadeck between 1276 and 1288 as a counter-castle against Runkel Castle, then held by a cousin. In 1321 Reinhard of Westerburg agreed to hand it to Archbishop Baldwin of Trier, who captured it in 1344; a 1346 treaty divided it before Reinhard sold his share. Parts, especially the north wing, were slighted in the Thirty Years' War and again in 1803.

The name comes from the castle's purpose: "eine Ecke zum Schaden der Burg Runkel", a corner from which to harm Runkel Castle. The settlement that grew around it took the same name. The building faces the Lahn and the opposite bank, a position chosen for its view of the rival castle.

The castle is easy to spot from the road and from public paths around the village, as it sits clearly above the river. The building is privately occupied, so only the exterior can be seen, but the elevated position makes it visible from several angles below.

During the 1800s, the main building served for a time as both the mayor's office and the village school. It is rare for a medieval fortification to have been used so directly for local government and children's education at the same time.