CASTEL-NAUDARY, a town of France, capital of an arrondissement of the same name, in the department of Aude, 21 miles west by north of Carcassonne. It is pleasantly situated on an elevation near the Canal du Midi; but is very indifferently built, having few public buildings worthy of notice except the church of St Michael, said to be the finest in the department. There are manufactures of woolen and cotton goods, leather, earthenware, and a considerable trade. It was founded by the Visigoths on the site of the ancient Sostomagus, and took the name of Castum Novum Arianorum—of which the present is a corruption. It suffered severely in the crusade against the Albigenses; but is chiefly noted in history for the battle fought there in 1632 between the forces of Louis XIII. and of Gaston Duc d'Orleans, in which the Duc de Montmorency was wounded and made prisoner, and soon after conveyed thence to Toulouse and executed. Pop. (1851) 9712.