Kajaani (käˈyänē) [key], Swed. Kajana, city (1996 pop. 36,795), Oulu prov., central Finland, on the Kajaaninjoki River. Forest products (including paper goods and cellulose) and sports equipment are manufactured. The city is also a road, rail, and water transportation center. Kajaani was chartered in 1651. The Kajaneborg fortress, around which the city grew, was taken by the Russians in 1716. Restored in 1937, the fortress is today a tourist attraction.