Grøtsundet

or is a strait between Tromsø Municipality and Karlsøy Municipality in Troms county, Norway. The 25 km long strait separates the islands of Reinøya and Ringvassøya from the mainland to the south. The strait has a width of 4-5 km. The strait is one of the main shipping lanes into the city of Tromsø, which lies about 10 km southwest of the strait.