Osterøy is an island municipality in Vestland county, Norway. It is located in the traditional district of Nordhordland. The municipality encompas…Osterøy is an island municipality in Vestland 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. The largest settlement is the village of Valestrandfossen with 1,219 inhabitants as of 1 January 2016.