capital of an arrondissement of the same name in the department of Tarn, France, 23 miles S.E. of Alby, stands in a pleasant and fertile valley, on both sides of the Agout, here crossed by two bridges. The town is ill-built, and the streets are narrow and crooked; but it has of late been much improved. The principal buildings are the town-hall, formerly the episcopal palace, the churches of St Benoît and Notre-Dame, two hospitals, barracks, theatre, and exchange. It is the seat of tribunals of primary instance and commerce, and of a Protestant consistory. Castres is celebrated for its manufactures, among which are woollen, linen, silk and cotton stuffs, soap, leather, paper, and iron and copper wares. It has also a considerable trade. Dacier, Rapin, and Sabatier were natives of this town. Pop. (1831) 19,098.