Eysturoyartunnilin is a large undersea road tunnel under the Tangafjørður sound in the Faroe Islands, connecting the island of Streymoy to the island of Eysturoy, meaning east island. It also crosses the southern part of Skálafjørður, and connects the towns of Runavík on the eastern side and Strendur on the western side of the fjord, and includes the world's first undersea roundabout in the middle of the network.

Streymoy is the largest and most populated island of the Faroe Islands. The capital, Tórshavn, is located on its southeast coast. The name means "island of currents". It also refers to the largest region of the country that also includes the islands of Hestur, Koltur and Nólsoy.