(German: Burgruine Aggstein, lit. “castle ruins of Aggstein”) is a ruined castle on the right bank of the Danube in Wachau, Austria. The castle dates to the 12th century.
Aggstein Castle is 480 metres (1,570 ft) above sea level. The castle ruins are situated at about 300 metres (980 ft) above the right bank of the Danube on an outcrop running from east to west. It is some 150 metres (490 ft) long and has a rock structure at both ends. The ruins are located within the municipality of Schönbühel-Aggsbach in the Melk District of Lower Austria.