Hailuoto is a Finnish island in the northern Baltic Sea and a municipality in Northern Ostrobothnia region. The population of Hailuoto is 924, makā¦Hailuoto is a Finnish island in the northern Baltic Sea and a municipality in Northern Ostrobothnia region. The population of Hailuoto is 924, making it the smallest municipality in Northern Ostrobothnia and the former Oulu Province in terms of population. The municipality covers an area of 205.65 km² of which 1.70 km² is inland water. The population density is 4.49/km². Of all the Finnish sea islands, Hailuoto is the third largest after Fasta Åland and Kimitoön.