Kalundborg (kä`lo͝onbôr), city (1992 pop. 15,304), Vestsjælland co., central Denmark, a port on the Kalundborg Fjord, an arm of the Store Bælt. It is a commercial, industrial, and communications center. Manufactures include chemicals, machinery, and ships. Founded c.1170, the city has a 12th-century church laid out in the form of a Greek cross. The novelist Sigrid Undset (1882–1949) was born in Kalundborg.