Rissa 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 Årnset. Other villages in the municipality include Askjem, Hasselvika, Husbysjøen, Rørvika, Råkvåg, and Stadsbygd.

The municipality of Rissen was established in 1860 when it was separated from the big municipality of Stadsbygd. Initially, Rissen had 3,733 residents. The spelling was later changed to Rissa. On 1 January 1905, the district of Lensvik (population: 1,019) on the west side of the Trondheimsfjord was separated from Rissa to form a municipality of its own. This left Rissa with 3,394 residents. On 1 January 1964, most of Stadsbygd (except the Ingdalen area) and the southern part of Stjørna were merged with Rissa to form a new, enlarged municipality of Rissa.

The Old Norse form of the name was Rissi. This was probably the old name of the brackish basin of Botn (literally "the bottom" of the fjord). Even though this is a heavily land-locked fjord with a river-like inlet from the Trondheimsfjord (it was probably a shallow bay in prehistoric times). The name is probably derived from the verb rísa which means "raise" or "rise". (The average water level of Botnen is today about 1.7 metres (5 ft 7 in) above mean sea level and the surface water is almost fresh from accumulated internal runoff.) The name of the municipality was historically spelled Rissen.

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