or is one of the longest rivers in Trøndelag county, in the central part of Norway. The long river flows through the municipalities of Røyrvik, Namsskogan, Grong, Overhalla, and Namsos before emptying into the Namsenfjorden. The river is the namesake for the whole Namdalen region. The river traditionally has been used for floating timber down from the forests to the town of Namsos, where the sawmills were located. Today, parts of the Namsen are regulated by several dams.
The total watershed is approximately and at Namsos, the water discharges into the fjord at about .
Fishing
The Namsen is considered one of the best Atlantic Salmon fishing rivers in the world, and is often called the "Queen of Rivers". Beginning in the 19th century, the British found the Atlantic salmon fishing to be excellent here, and the river became a major tourist attraction. Catches above are not unusual. The Namsen is a wide river and is thus often fished from small boats using a method called "harling". This method consists of trolling a lure while the boat moves slowly from bank to bank and drifting downstream. Thus, the salmon meet the lure as they swim upstream.