Rjukan Falls (English)[1] or Rjukanfossen (Norwegian) is a waterfall in the western part of the Vestfjorddalen valley in Tinn Municipality in Telemark county, Norway.

The 104-metre (341 ft) tall waterfall is located on the river Måna, about 5 kilometres (3.1 mi) to the west of the town of Rjukan.

In 1905, the waterfall and surrounding river were harnessed by the Vemork hydro-electrical power plant to produce power for the saltpetre production at a nearby Norsk Hydro factory.

[2] The waterfall is named Rjukanfossen in Norwegian (Old Norse: Rjúkandi).

[2] The last element is a later addition to the name which comes from the Norwegian word fossen which means "the waterfall".