Storfosna[1] is a populated island in Ørland Municipality in Trøndelag county, Norway.

The 11-square-kilometre (4.2 sq mi) island is located between the islands of Kråkvåg and Garten north of the mouth of the Trondheimsfjorden.

The traditional district of Fosen is named after this island.

[2] The island is connected to the island of Kråkvåg by a causeway and bridge, and is connected to Garten (and the mainland) by a car ferry.

The local and county governments are planning to build an undersea tunnel connecting Storfosna to the island of Garten (which is connected to the mainland by road).