Festungsberg is a mountain in the city of Salzburg, Salzburgerland, Austria. Its summit at about 542 m (1,778 ft) is the site of Hohensalzburg Castle.
The mountain is located in the south of the Altstadt or Old Town quarter. It forms the northern rim of the Salzkammergut range within the Northern Limestone Alps.
Archaeological findings date back to the Celtic La Tène culture, and the area was already settled during the days of the Roman city of Iuvavum until the invasion of King Odoacer of Italy into the Province of Noricum in 488. About 715 Bishop Rupert of Salzburg established the Benedictine Nonnberg Abbey at the eastern foot of the mountain. Archbishop Gebhard had a first castle built at the top during the Investiture Controversy about 1077. Formerly used for vineyard cultivation by the monks of St Peter's Abbey, the slopes are nowadays mostly wooded.