Giessen (gēˈsən) [key], city (1994 pop. 73,705), Hesse, central Germany, on the Lahn River. It is an industrial center and rail junction. Its manufactures include machinery, textiles, rubber goods, and tobacco products. Iron ore is mined nearby. Giessen was chartered by 1248 and became the chief town of Upper Hesse. The city was heavily damaged in World War II. It is the seat of a famous university (founded 1607), where the chemist Justus von Liebig taught (1824–52).