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Öja is an island and a former municipality in the Finnish countryside Central Ostrobothnia. Today it belongs to the city of Kokkola.
Öja is located in the Gulf of Bothnia in the archipelago off the coast of Kokkola. Also indicated by the name, which is derived from the Swedish word for "island". The island Öja has an area of 90 square kilometers. This makes it the eighth largest island in the Finnish Baltic Sea waters. The western part of the island belongs to the municipality Larsmo, the eastern to Kokkola. In 1969, the narrow sound, the Öja was separated from the mainland, separated by the construction of a dam from the sea and converted to freshwater Öjanjärvi ( Öjasjön ).
Öja broke up in 1932 as an independent community of Kaarlela, the municipality that originally surrounded the town Kokkola. 1969 Öja was reunited with Kaarlela with which it was amalgamated in Kokkola in 1977. The municipality had last Öja an area of 50.0 square kilometers and 656 inhabitants ( 1963). In 1960, 98.9 % of the population were Finland Sweden.