Burgruine Kollmitz, Medieval castle ruins and museum in Raabs an der Thaya, Austria.

Burgruine Kollmitz is a ruined spur castle on a steep rock spur above a loop of the Thaya east of Raabs an der Thaya. Its surviving structures include two round corner towers, a semicircular gate tower with a pointed-arch portal, a bergfried, a hunger tower and remains of a two-storey residential building.

Kollmitz Castle was first documented in the 13th century, and dendrochronology dates its bergfried to 1319. In the 14th century it housed a district court. From 1411 the Hofkirchen family held it until Wolfgang von Hofkirchen died in Prague exile in 1611. After changing owners, it passed in 1708 to Franz Anton von Quarient und Raal, who let it decay.

The castle is linked for about 300 years with Drösiedl, which from 1570 was rebuilt as a Renaissance castle; Kollmitz might even have been abandoned had other owners not lived there after Hofkirchen's expulsion. Since 1974 the Verein zur Erhaltung der Burgruine Kollmitz, founded by composer and local historian Herbert Loskott, has cared for the ruins, and in summer a Jausenstation (snack station) operates on the site.

The ruins stand on a steep rock spur above a loop of the Thaya; the valley road along the river gives a good view of the whole complex. A Jausenstation (snack station) operates on the ruins in summer. The site is cared for by the Verein zur Erhaltung der Burgruine Kollmitz, founded in 1974.

The castle had a predecessor on the opposite side of the valley, west of Kollmitzgraben, where its site is barely recognisable today. That earlier castle, probably named Hauenstein, was occupied for only about 150 years before the new Kollmitz was built 400 metres to the east. All mentions of Chalmunze before 1250 refer to the Kollmitzberg near Amstetten, not to this castle.