The Žumberak Mountains (Croatian: Žumberačka gora, Slovene: Gorjanci, historic German name: Uskokengebirge) is a range of hills and mountains in northwestern Croatia and southeastern Slovenia, extending from the southwest to the northeast between the Krka and the Kupa.
It covers an area of 430 km2 (170 sq mi). The geographically unified massif consists of two parts, separated by the Bregana and Žumberak rivers (Croatian: Žumberačka rijeka). The northeastern part is the Samobor Hills (Croatian: Samoborsko gorje) with the foothills. The central and western part is named Žumberak Hills (Croatian: Žumberačko gorje, Žumberak). Its northwesternmost part, named Gorjanci, lies in Slovenia. The highest peak of the range is Sveta Gera (Trdina Peak) on the border between Croatia and Slovenia, being 1,178 m (3,865 ft) high. Since 1999, an area of the range in Croatia has been protected as the nature park Žumberak–Samobor Hills.