Königsfelden Monastery is a former Franciscan double monastery, which housed both a community of Poor Clare nuns and one of Franciscan friars, living in separate wings, in the municipality of Windisch in the canton of Aargau in Switzerland. It was founded in 1308 by the Habsburgs. In the course of the Protestant Reformation in Switzerland in 1528 it was secularized, and the complex was then the residence of the bailiffs of Bern.
Since 1868 the former monastic buildings have served as a psychiatric clinic. The monastery church was converted into a museum in 2009. It contains a set of 14th-century stained glass windows which, together with the windows in the Cathedral of Bern, are considered the most valuable in Switzerland.
On May 1, 1308, King Albert I of Austria was murdered by his nephew John Parricida in the community of Windisch. In memory of this event his widow, Elizabeth of Carinthia, founded the monastery about 1310-11 at the site, approximately 200 meters (660 ft) from Brugg. The monastic complex centered around the contemplative life of the nuns, while the small community of friars tended to both their spiritual needs and that of the surrounding community.
Albert and Elisabeth’s oldest daughter, Agnes of Austria, the widow of King Andrew III of Hungary, moved to Königsfelden in 1317 and helped it to thrive, but did not join the monastery.