Sedan (sədäNˈ) [key], town (1990 pop. 22,407), Ardennes dept., NE France, on the Meuse River. A noted textile center since the 16th cent., Sedan also has metal and brewing industries. The town became part of French crown lands in 1642. It was a Protestant stronghold in the 16th and 17th cent., and a noted Calvinist academy was located there. Sedan was the site of the decisive French defeat (1870) in the Franco-Prussian War and the surrender of Napoleon III. The town saw heavy fighting in World War I and was the point of the first German breakthrough (1940) in the invasion of France in World War II.