Liebenstein Castle, Medieval castle in Thuringia, Germany.

Liebenstein Castle is a ruined spur castle on a 385-metre hill above the village of Liebenstein in the Ilm-Kreis. Its surviving core, built before 1346 under Count Günther XXI of Schwarzburg, joins a five-storey west tower to a long residential block with rounded outer corners and a pointed-arch portal. The lower storeys have slit windows; larger rectangular windows were inserted in the 16th century.

Liebenstein Castle was first mentioned in 1282 as the origin name of Schwarzburg ministeriales. From 1303 to 1367 it belonged to the counts of Käfernburg-Schwarzburg; Count Günther XXI had it rebuilt during the Thuringian Counts' War (1342–1346). In 1367/69 it passed to the Wettins, who granted it as a hereditary fief to the Witzleben family. Around 1600 inheritance divisions brought decline; the Witzleben line died out in 1820 and the castle went to Saxe-Gotha, serving as an administrative seat until 1859.

The castle's name comes from the ministeriales family von Liebenstein, first recorded in 1282. From 1367/69 the Wettins granted it as a hereditary fief to the Witzleben family, who lived in the front building while the rest served as a prison. The Witzleben line died out in 1820, and the castle passed to Saxe-Gotha.

The ruin stands on a 385-metre spur above the village of Liebenstein, surrounded on three sides by a 12-metre-deep neck ditch. The tower and residential building were secured and their wall tops repaired up to 2000, and the retaining wall from 2010. The courtyard was filled in during the 20th century and now lies about a metre above its original level.

The castle controlled a road to the Thuringian Forest passes and its sphere of influence covered thirteen villages. A 2002–2003 excavation on the north side of the residential building found a 4-metre-deep older wall, possibly the outer ring wall, below today's ground level.