Schloss Hollenburg (Slovene: Humberk) is a medieval castle near Köttmannsdorf in Carinthia, Austria. It is located on a rock of the northern slope of the Drava valley. One Swiker, Lord of Hollenburg in the Duchy of Carinthia was first documented as a witness in the 1142 deed of the foundation of Viktring Abbey. He may have been a liensman of the ducal House of Sponheim; his son Reginher is mentioned as Lord of Steuerberg, he accompanied King Conrad III of Germany on the Second Crusade in 1147 and later appeared as a ministerialis of Margarve Ottokar IV of Styria.
The castle was of strategical importance due to its location at a Drava river crossing and the road to the Loibl Pass and the March of Carniola. Upon the extinction of the Hollenburg dynasty in 1246, it passed to the Styrian Lords of Pettau, in 1438 it was inherited by the House of Stubenberg. The structure had been severely damaged by the 1348 Friuli earthquake.