Burg Ehrenfels, Medieval castle ruins in Sankt Radegund bei Graz, Austria.

Burg Ehrenfels is a castle ruin in Sankt Radegund bei Graz with a rectangular stone tower and thick defensive walls. The structure sits on a hillside overlooking the valley and landscape below.

The castle was built in the early 13th century by Otto II von Graz to control an important trade route. In the 15th century it changed hands and lost its original strategic function.

The name Ehrenfels, meaning 'honour rock', was adopted by Otto II von Graz in 1229, and the castle controlled the busy Römerweg route toward Semriach and Passail. The family died out with Hans von Ehrenfels in 1442, and from 1424 the site passed to Konrad von Kraig, then in 1449 to Hans von Stubenberg. Restoration from 1964 made parts habitable again; the ruin is privately owned.

The ruin stands at 481 metres above sea level in the municipality of Sankt Radegund bei Graz, not at the foot of the Schöckel. It is in private ownership, and parts were made habitable again after restoration began in 1964. Access is via marked hiking paths; no visitor facilities are documented.

The castle was built by a ministerial, a noble official who acted on behalf of a prince rather than ruling in his own right. This shows that important fortifications were not always built by rulers themselves but often by their trusted administrators.