Åfjord is a municipality in Trøndelag county, Norway. It is part of the Fosen region. The administrative centre of the municipality is the village of Årnes. Other villages in the municipality include Revsnes, Roan, Bessaker, Harsvika, and By. Åfjord is located on the northwestern side of the Fosen peninsula, northwest of the city of Trondheim. It is located between the municipalities of Ørland and Osen and to the west of Steinkjer, with Indre Fosen to the south.
The municipality is the 74th largest by area out of the 356 municipalities in Norway. Åfjord is the 196th most populous municipality in Norway with a population of 4,252. The municipality's population density is and its population has increased by 0.2% over the previous 10-year period.
The municipality of Aafjord was established on 1 January 1838 (see formannskapsdistrikt law). On 26 March 1870, a royal resolution moved a small, unpopulated part to Aafjord to the neighboring municipality of Bjugn. On 1 January 1896, the southwestern coastal area of Aafjord (population: 1,529) was separated to form the new municipality of Jøssund. This left Aafjord with 2,419 residents. On the same date, the name of Aafjord municipality was changed to just Aa. The spelling was later changed to Å. On 13 July 1934, the name of the municipality was changed from "Å" to "Åfjord". After that, the administrative centre in the municipality was referred to as "Å" or "Å i Åfjord".
During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. On 1 January 1964, the neighboring municipalities of Stoksund (population: 2,643) and Åfjord (population: 1,515) to form the new, larger municipality of Åfjord. On 1 November 1980, the postal service changed the name of the municipal center from "Å i Åfjord" to "Årnes".
On 1 January 2018, the municipality switched from the old Sør-Trøndelag county to the new Trøndelag county.
On 1 January 2020, the neighboring municipalities of Roan and Åfjord merged into one large municipality called Åfjord.