Rjukan is a town in Tinn Municipality in Telemark county, Norway. The town is also the administrative centre of Tinn Municipality. The town is located in the Vestfjorddalen valley, between the lakes Møsvatn and Tinnsjå. The municipal council of Tinn declared town status for Rjukan in 1996. The town is located about 10 kilometres (6.2 mi) to the west of the village of Miland and about 20 kilometres (12 mi) to the northwest of the village of Tuddal.

Telemark is a county and a current electoral district in Norway. Telemark borders the counties of Vestfold, Buskerud, Vestland, Rogaland and Agder. In 2020, Telemark merged with the county of Vestfold to form the county of Vestfold og Telemark. On 1 January 2024, the county of Telemark was re-established after Vestfold og Telemark was divided again.