Šoštanj is a town and municipality in northern Slovenia. It was first mentioned in written documents dating to around 1200 as Schönstein in relation to its castle. As a market town it was first mentioned in 1348. It was given town status in 1919 and until the 1960s was the center of the Šalek Valley (Slovene: Šaleška dolina). In 1963 nearby Velenje became the administrative center. Šoštanj again became a municipal center in the late 1990s. The town has a long leather-working history, with industrial-scale activity going back to 1788. The factory was owned by the Woschnagg family, a Germanized branch of the Vošnjak family, until it was nationalized in 1945. The processing factory was closed down in 1999. A leather industry museum is now open in the town.