Kalmar (kälˈmär) [key], city (1990 pop. 30,820), capital of Kalmar co. (1995 pop. 144,060), SE Sweden, on the Kalmarsund (an arm of the Baltic Sea) opposite Öland Island. It is a commercial, industrial, and tourist center and is connected by ferry with Öland. Manufactures include machinery, matches, glass, processed food, and ships. It has been an important trade center since the 8th cent. The Kalmar Union was negotiated there in 1397. Kalmar has a 13th-century castle, Kalmar Slott, which withstood numerous sieges in the Danish-Swedish wars of the 16th-17th cent. The name is also spelled Calmar.