Namsen (Norwegian) or Nååmesje (Southern Sami)[1] is one of the longest rivers in Trøndelag county, in the central part of Norway.

The 228-kilometre (142 mi) long river flows through the municipalities of Røyrvik, Namsskogan, Grong, Overhalla, and Namsos before emptying into the Namsenfjorden.

The Namsen river itself starts when the water passes through the dam on the northwest side of the lake Namsvatnet in Røyrvik Municipality.

[3] The total watershed is approximately 6,298 square kilometres (2,432 sq mi) and at Namsos, the water discharges into the fjord at about 285 cubic metres per second (10,100 cu ft/s).

Beginning in the 19th century, the British found the Atlantic salmon fishing to be excellent here, and the river became a major tourist attraction.