Siegen, city (1994 pop. 111,845), North Rhine–Westphalia, W Germany, on the Sieg River. Iron ore is mined nearby, and the city has iron foundries. Other manufactures include leather goods and machinery. Siegen was the residence of the princes of Nassau-Siegen from 1606 to 1743. The city was severely damaged in World War II. Noteworthy buildings include two castles and the Nikolaikirche, a 13th-century church. Flemish painter Peter Paul Rubens was born (1577) in Siegen.