Schloss Mannsberg, Medieval castle in Kappel am Krappfeld, Austria.

Burg Mannsberg is a medieval hilltop castle at 691 metres above sea level in Mannsberg, Kappel am Krappfeld. Its highest part is the main castle on a polygonal plan, enclosed by a high ring wall, with a four-storey trapezoidal palas built in the 14th century. The irregular west wing with courtyard arcades dates from 1549, and a three-storey gate tower leads via a zwinger to the palas.

Mannsberg was first recorded as loco Magnesperc between 1065 and 1075, when the noble Adalbero gave it to the Bishopric of Brixen under Bishop Altwin. The name means "castle of Mangan", a man not attested in any document. From 1190 the ministeriales Schrankbaum held it for the Counts of Ortenburg, and in 1301 Konrad Schrankbaumer received it as a fief of the Carinthian dukes.

The castle chapel is decorated with stucco work dated 1711. The interior rooms were shaped between the 16th and 18th centuries; on the third floor a beam ceiling carries the coat of arms of the Khevenhüller-Stubenberg family. A small chaplaincy building was added east of the main building in 1627.

The castle is in private ownership and has been since 1874, so the grounds and interiors are not open to visitors; the building can only be viewed from outside. It stands at 691 m above sea level on the southern end of a ridge above a wooded valley in the Mannsberg hamlet of Kappel am Krappfeld. The lower ruin Altmannsberg lies about 200 m south, somewhat lower on a rocky knoll.

About 200 metres south of the main castle, on a rock outcrop, stand the remains of the lower castle Altmannsberg, built on an irregular hexagonal plan. Its ring wall, originally two storeys high and 1.30 metres thick, has a single round-arched gate at ground level and numerous arrow slits. A residential wing was inserted into the courtyard in the 13th century; by 1688 the site was recorded as an abandoned tower.