Castres is a commune, and arrondissement capital in the Tarn department and Occitanie region in southern France. It lies in the former French province of Languedoc.Castres is (after Toulouse, Tarbes and Albi) the fourth largest industrial centre of the predominantly rural Midi-Pyrénées région and the largest in that part of Languedoc lying between Toulouse and Montpellier.Castres is noted for being the birthplace of the famous socialist leader Jean Jaurès and home to the important Goya Museum of Spanish painting.DemographyIn 1831, the population of Castres was 12,032, making it the largest town of the department of Tarn. One of the few industrial towns in the region of Albigeois, the population of the commune proper grew to 19,483 in 1901, and 34,126 by 1954 (44,161 inhabitants in the metropolitan area). However, with the decline of its industries, population growth diminished. Albi surpassed Castres as the most populous metropolitan area of Tarn. The population of Castres is now stagnating: after small growth in the 1970s and 1980s, it registered zero growth in the 1990s.