Borgholm (bôr´yəhôlm´), town (1990 pop. 3,169), Kalmar co., SE Sweden, on Öland Island and on the Kalmarsund, an arm of the Baltic Sea. It is a seaside resort. Of note are the ruins of Borgholm castle (13th cent.; rebuilt 16th–17th cent.), destroyed by fire in the early 19th cent.