Burgruine Pfannberg, Medieval castle ruins in Frohnleiten, Austria

Burgruine Pfannberg is a ruined hilltop castle on a ridge of the Trötsch above Frohnleiten. A ring wall follows the edge of the terrain, enclosing a three-storey palas of around 1400 in the north and the rubble of a 13th-century seven-sided bergfried blown up in the second half of the 20th century. In the east, only part of the chapel apse wall survives.

Construction began in the early 13th century when the Peggau lords needed a larger stronghold than their previous dwelling. The fortress was expanded over time before eventually facing decline and deterioration in later centuries.

The chapel's north wall held a fresco from the second quarter of the 15th century showing the Coronation of Mary with Hugo von Montfort, who died in 1423, and his family. It was removed in 1954 and is now kept in the Universalmuseum Joanneum in Graz. Only part of the apse wall remains on the site.

Access to the ruins is from the south over a saddle where the former Meierhof stood; the inner gate is blocked by fallen masonry, so the courtyard is entered through the preserved gate tower. The site lies on a hilltop of the Trötsch above Frohnleiten, in the Pfannberg cadastral district. Conservation and restoration have been carried out repeatedly since 1952.

The chapel fresco, painted in the second quarter of the 15th century, showed the Coronation of Mary with Hugo von Montfort, who died in 1423, and his family. It was removed from the north chapel wall in 1954 and is now kept in the Universalmuseum Joanneum in Graz, so the wall itself is bare.