Sundøy or Sundøya is a village in the municipality of Leirfjord in Nordland county, Norway. The village is located about 5 kilometres (3.1 mi) south of Leland, and it has a population of about 120 people. It is located on the north side of the Vefsnfjorden on the northeastern part of the island of Alsta, east of the Seven Sisters mountains, which isolate it from the rest of the island.