Schloss Horn, Medieval castle in Horn, Austria.

Schloss Horn stands in the southeast corner of the walled town of Horn, Lower Austria, where the Mödringbach flows into the Taffa. The complex is a three-winged building with a massive northeast tower and the southeast corner tower of the town's first fortification, the Diebsturm, both from the 12th/13th century. Medieval core walls survive in the south, west and north wings, and a projecting polygonal corner tower was added to the northwest in the mid-19th century.

A town castle was founded in the 12th century and remained a princely seat until 1210. It then passed to the Maissauer family until 1440, followed by the Puchheims, who in 1539 added casemates and stables east of the original wall. After 1620 it belonged to the Muschinger and Kurz families, and since 1676 to the Hoyos-Sprinzenstein line.

The castle passed by marriage to the Hoyos family in 1676 and has stayed with its Hoyos-Sprinzenstein line since; the family name is still tied to the building. Part of the complex now serves as an administrative building, so the former seat of local lordship is in everyday official use.

The castle stands in the southeast corner of Horn's walled old town, where the Mödringbach flows into the Taffa, about 340 metres west of the town centre and 312 metres above sea level. Parts of the building are used as administrative offices, so the wings are not open to visitors as a museum; the exterior, the massive northeast tower and the Diebsturm corner tower can be seen from the surrounding streets.

The northeast tower of the former castle is unusually massive and broad, and the southeast corner tower of the town's first fortification is known as the Diebsturm (Thief's Tower); both date from the 12th or 13th century. The castle has belonged to the Hoyos family, Hoyos-Sprinzenstein line, since 1676.