Bad Kreuznach (bät kroitsˈnäkh) [key], city (1994 pop. 42,960), Rhineland-Palatinate, W Germany, on the Nahe River. Its manufactures include optical instruments, tires, machinery, and leather. Bad Kreuznach was probably settled in the Stone Age. Its radioactive salt baths have been frequented since Roman times, when it was a garrison town.