The Måna or Måne is a river in Tinn Municipality in Telemark county, Norway. The 32 km river flows from the lake Møsvatn through the Vestfjorddalen valley and the town of Rjukan to the large lake Tinnsjå near the village of Miland. It is part of the Skiensvassdraget drainage basin. The entire river has a total drop in elevation of 727 m from Møsvatn to Tinnsjå, notably including the Rjukan Falls, a large waterfall that has also been a major tourist attraction. This area has been developed in five power stations with a total installation of 506 MW and a total average annual production of 2237 GWh. The largest power stations are Vemork and Såheim.