Herøy is a municipality in Nordland county, Norway. It is part of the Helgeland traditional region. The administrative centre of the municipality is the village of Silvalen. The municipality is located about west of the town of Sandnessjøen.The 64km2 municipality is the 407th largest by area out of the 426 municipalities in Norway. Herøy is the 343rd most populous municipality in Norway with a population of 1,788. The municipality's population density is and its population has increased by 6.3% over the last decade.General informationThe municipality of Herøy was established in 1864 when it was separated from Alstahaug. Initially the population of Herøy was 2,438. On 1 July 1917, the northern district of Herøy (population: 1,530) was separated from Herøy to become the new municipality of Nordvik. This left Herøy with 2,555 residents.On 1 January 1962 the part of Herøy on the island of Dønna (population: 19) was transferred to the new municipality of Dønna. On 1 January 1965 the Husvær/Sandværet island groups (population: 461) were transferred from Alstahaug to Herøy.