Fosnes was established as a municipality in the old Nord-Trøndelag county on 1 January 1838. On 1 January 1871, the western district of Fosnes was separated to form the new municipality of Flatanger. This left Fosnes with 2,655 residents. On 1 January 1889, a small area of Fosnes was transferred to the neighboring municipality of Vikten. Then on 1 January 1913, the western part of Fosnes was separated to form the new municipality of Otterøy. This left the much smaller municipality with 1,107 residents. During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. On 1 January 1964, the Finnanger area of Fosnes on the northern part of the island of Otterøya was transferred to the new municipality of Namsos. In 2018, it became part of the new Trøndelag county which replaced the old Nord-Trøndelag county. On 1 January 2020, Fosnes became a part of the neighboring Namsos Municipality. This happened because on 16 June 2016, the municipalities of Fosnes, Namsos, and Namdalseid voted to merge into a new, larger municipality as part of a large municipal reform across Norway.
Name
The municipality is named after the old Fosnes farm, since the first Fosnes Church was built there. The first element is fólgsn which means "hiding place" and the last element is nes which means "headland". Historically, the name was spelled Fosnæs.
Coat of arms
The coat of arms was granted on 13 November 1992. The arms show a black oarlock from a rowing boat on a yellow background. Fosnes is a coastal municipality and rowing boats were the main form of transportation in the former centuries. The first proposal for arms of Fosnes were taken in 1989, when the council launched a contest to develop arms. Several proposals were received but none was acceptable to or the council, or the Norwegian Heraldic Society, as the proposals were not made according to heraldic rules. Finally the Society proposed the above arms, which were acceptable to the council.
Fosnes was a coastal municipality located along the Foldafjord, north of the town of Namsos. The municipality includes the island of Jøa, part of the island of Elvalandet, and part of the mainland. The second deepest lake in Europe, Salvatnet, and the lake Mjosundvatnet are both located in the eastern part of the municipality.
The municipal council of Fosnes is made up of 13 representatives that are elected to four year terms. The party breakdown of the final municipal council was as follows: