Castres (käsˈtrə) [key], city (1990 pop. 46,292), Tarn dept., SW France, on the Agout River. It has been a textile center since the 13th cent., and its machine tools are known worldwide. Wood products, especially furniture, and pharmaceuticals are also manufactured. Once the site of a Roman encampment, Castres grew around a Benedictine monastery founded in A.D. 647. Protestantism took hold in the 16th cent. but was suppressed by Louis XIII. The revocation (1685) of the Edict of Nantes jeopardized the city's economy by expelling Protestants, but Castres prospered anew under Louis XIV. There are several 17th- and 18th-century churches.