Runkel Castle, Medieval castle in Runkel, Germany

Runkel Castle is a ruined hill castle above the Lahn in Runkel, Hesse, about 35 to 40 metres above the valley floor. Rough grey stone forms a cluster of tall square towers and connecting walls with small rectangular windows; one square tower stands at the left, a taller one with a flagpole beside it, and two round-arched openings sit near the top of a wall next to a large rectangular tower. The upper castle remains a ruin, while the lower castle was rebuilt.

Runkel Castle was first mentioned in 1159, when it belonged to Siegfried I von Runkel; it was probably built slightly earlier to guard the Lahn crossing, then a ferry. In 1276 Siegfried V expelled his cousin Heinrich, who built Schadeck Castle opposite from 1288. Imperial troops under Graf Isolani burned the castle and town on 15 October 1634; the upper castle was never rebuilt, while the lower castle was repaired.

The castle's name likely comes from the Celtic "Run-kall", meaning rock mountain, for the hill the Celts already used. The Wied-Runkel line took its title from the castle after Dietrich IV inherited the County of Wied through his marriage to Anastasia of Isenburg-Wied. Today the lower castle holds a museum, a chapel and an archive, while the owner's great-uncle, Metfried Prince of Wied, keeps a private wing there.

The upper castle is a ruin and closed to visitors, but the main keep can still be entered. The lower castle, rebuilt in 1642, holds the museum, chapel and archive. The site lies on the Lahn about six kilometres east of Limburg an der Lahn, roughly 35 to 40 metres above the valley.

The castle's name may come from the Celtic "Run-kall", meaning "rock mountain", as the hill had already drawn Celtic attention. In 1440 work began on a stone bridge over the Lahn, but a dispute over toll revenues delayed its completion until 1448.