Undersåker is a locality in Åre Municipality, in Jämtland County, Sweden. Undersåker lies at 445 m above sea level, 3.1 km from the Sylan mountains. It has 645 inhabitants (2023). The nearest city is Östersund, 71 km to the east. Among the landmarks around are Åre Old Church (12.5 km), Undersåkers kyrka (6.9 km) and Kalls kyrka (17.5 km). Among the natural features are Ristafallet (4.9 km).