Alnö ("the aln-ey") is an island in the Gulf of Bothnia just outside Sundsvall in Medelpad, Sweden. It has an area of 67.79 km2 and a permanent population of 8,298. The island is 15 km long and 6 km wide on the widest spot. It is connected to the mainland by a 1,042-meter-long (3,419 ft) bridge, which was the longest bridge in Sweden when it was opened in 1964.