Osterøy is an island municipality in Hordaland county, Norway. It is located in the traditional district of Nordhordland. The municipality encompasses most of the island of Osterøy. The administrative centre of Osterøy is the village of Lonevåg in the central part of the island, while the settlement with the largest population is the village of Valestrandfossen with 1,101 inhabitants as of 1 January 2012.