Köthen, city (1994 pop. 31,860), Saxony-Anhalt, central Germany. Köthen has lignite mines, sugar refineries, textile mills, chemical factories, and heavy engineering industries. The city is also a rail junction, and has an airport. It is home to a school of chemical engineering and a teachers' college. Known in 1115, Köthen was from 1603 to 1847 the residence of the dukes of Anhalt-Köthen, at whose court Johann Sebastian Bach was musical director from 1717 to 1723. A former spelling was Cöthen.