Albrechtsberg Castle, Protected medieval castle in Loosdorf, Austria.

Albrechtsberg Castle is a fortress on elevated terrain near Loosdorf in Lower Austria, featuring thick stone walls, several towers, and a layout designed for both residence and defense. The structure commands the surrounding landscape and is visible from many directions.

Albrecht von Perg (1120–1168) of the Herren von Perg und Machland built and named the castle; his wife, a countess von Schalla, brought estates in the Pielachtal into the marriage. By 1311 it belonged to the Fleischeß, a Lower Austrian knightly family, who had the originally Romanesque chapel of St. Achatius rebuilt in Early Gothic form in 1337 and sold the castle to Hans von Ybbs in 1357. After the Perg line died out, half passed to the Babenbergs and half to the county of Plain, later Schaunberg. In 1581 a Renaissance castle was built over the medieval fortress.

The castle takes its name from Albrecht von Perg (1120–1168), who built the original hilltop castle. The chapel, dedicated to Saint Achatius, was rebuilt in early Gothic style in 1337 under the Fleischeß family and later reconsecrated as a Catholic chapel after the Protestant revolt. Between 1925 and 1936, Karl Anton Rohan published the Europäische Revue from the castle.

The grounds are accessible year-round, with guided tours in German and English available by advance booking. Visitors should wear sturdy shoes since pathways and stairs are uneven and there are elevation changes throughout the site.

Between 1925 and 1936, Karl Anton Rohan edited the journal Europäische Revue at the castle. The building has belonged to the Weinberger family since 1995 and is being renovated step by step; tenants live there regularly.