Burgruine Dietrichstein, Medieval castle ruins in Feldkirchen in Kärnten, Austria.

Burgruine Dietrichstein is a ruined castle above the Glan valley near Feldkirchen. Of the former stronghold, parts of the Romanesque ring wall survive on the north side up to about two metres high, and late Gothic masonry is visible on the east side. The south-west side drops steeply into the valley, while two ramparts and three ditches protect the north-east side. At the foot of the hill stands a two-storey, cube-shaped castle building with a roof turret and a Roman tomb relief from the 2nd century built into the ground floor.

First mentioned in 1103 in connection with the knight Dietrich, the castle was held by the Eppenstein dukes' ministerials until the Hochstift Bamberg acquired it and Feldkirchen in 1166. It guarded the Glantal road and the later market of Feldkirchen. Around 1335 Margarethe Maultasch destroyed it, and it was rebuilt before 1370. In 1483 Pankraz von Dietrichstein surrendered after a six-month siege to Matthias Corvinus's troops, who razed it; it was finally demolished in 1491 and has remained a ruin.

The Dietrichstein family crest featured a vine knife, recalling medieval viticulture in the area. The castle controlled the Glantal road, part of the Venedigerstraße between Vienna and Venice, and protected the later market of Feldkirchen. The nearby Dietrichsteiner See still belongs to the estate.

The ruin stands on a rock slope above the Glan valley near Feldkirchen. The south-west side drops steeply into the valley, while the north-east side is protected by two ramparts and three ditches. Parts of the Romanesque ring wall survive on the north side to about two metres high, and late Gothic masonry is visible on the east side.

The north-east side was protected by two ramparts and three ditches, while the south-west side drops steeply into the Glan valley. Parts of the Romanesque ring wall still stand about two metres high on the north side, and late Gothic masonry is visible on the east side.