Fosen is a traditional district in Trøndelag, consisting of the municipalities Osen, Roan, Åfjord, Bjugn, Ørland, Rissa, Agdenes, Snillfjord, Hemne, Hitra and Frøya. The district is dominated by forested valleys, lakes, coastal cliffs but also shallow areas, and in the interior mountains reaching up to 675 m elevation. The western coast has many skerries and some islands, such as Stokkøya in Åfjord. There are some good salmon rivers, and sea eagles and other sea birds are very common along the coast, notably on the shallow area near Ørland (Grandefjæra). The west coast has mild winters, and some locations (just west of the mountains) receive on average more than 2,000 mm of precipitation per year. Part of the Scandinavian coastal conifer forests (No: Kystgranskog) are located in the valleys of the peninsula, and smaller areas are classified as temperate rainforest with 67 nature reserves. The largest nature reserve is Øyenskavelen (5,316 hectare), with many nature types including undisturbed forest, some of it classified as rainforest.
Fosen also has a folkehøgskole (folk high school), Fosen Folkehøgskole. It teaches unusual subjects such as sailing and building traditional Norwegian boats (close to Viking ships), organic agriculture, traditional Norwegian arts and crafts, nature life, etc.