Ossiach Abbey, Benedictine monastery in Ossiach, Austria.

Ossiach Abbey is a Benedictine monastery in Ossiach near Lake Ossiach in Austria. The complex combines Romanesque foundations with Gothic modifications and Baroque decoration throughout its church and surrounding structures.

Count Ozi and his wife Glismod founded the abbey shortly before 1028, and the first monks came from Niederaltaich Abbey in Bavaria. Ozi's son Poppo, Patriarch of Aquileia, placed it under Aquileia's influence, confirmed by Emperor Conrad II in 1028. The Vogtei passed to the Babenbergs in 1192 and to the Habsburgs in 1282. Emperor Joseph II dissolved the abbey in 1783, after which the buildings served as barracks and were largely demolished in 1816.

The abbey church, now the parish church, holds stained glass windows on the organ gallery donated in 1905 by the province of Galicia and Lodomeria; the writer Karl May gave two windows the same year, though research suggests he never visited. Polish pilgrims long venerated the alleged tomb of King Bolesław II at the north wall, where Polish soldiers placed a memorial stone in 1945/46. The abbey is one of the venues of the Carinthian Summer music festival.

The abbey church still serves the local parish, so it is best visited outside service times. The former monastic buildings, owned by the Carinthian administration since 1995, stand behind a fringe of reeds at the southern shore of Lake Ossiach. Look for the Roman marble relief with the Latin inscription on the northern church wall.

A tomb in the church's northern wall reportedly holds the remains of King Bolesław II of Poland, who lived here as a mute penitent. This connection links the Austrian abbey to Polish royal history through an unusual personal fate.