Åfjord is a municipality in Sør-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, Harsvika, and By. Åfjord is located on the northwestern side of the Fosen Peninsula, northwest of county capital of Trondheim between the municipalities of Bjugn and Osen and to the west of Verran in the neighboring county of Nord-Trøndelag.
The municipality of Aafjord was established on 1 January 1838 (see formannskapsdistrikt). On 26 March 1870, a royal resolution moved a small, unpopulated part to Aafjord to neighboring Bjugn. On 1 January 1896, the Jøssund area was separated from Aafjord to form a municipality of its own, leaving Aafjord with 2,419 residents. On the same date, the name of Aafjord 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". On 1 January 1964, the municipality of Stoksund was merged with Åfjord to form the new, larger municipality of Åfjord. Prior to the merger, Åfjord had 2,643 residents. On 1 November 1980, the postal service changed the name of the municipal center from "Å i Åfjord" to "Årnes".