CASTELNAUDARY, a town of south-western France, capital of an arrondissement in the department of Aude, 22 m. W.N.W. of Carcassonne, on the Southern railway between that city and Toulouse. Pop. (1906) 6650. It is finely situated on an elevation in the midst of a fertile and well-cultivated plain; and its commercial facilities are greatly increased by the Canal du Midi, which widens out, as it passes the town, into an extensive basin surrounded with wharves and warehouses for the timber used in the upkeep of the canal. The principal buildings are the law court, the hôtel de ville, and the church of St Michel, dating from the 14th century; none of these offers any feature of unusual interest. There are a number of flour-mills, as well as manufactories of earthenware, tiles and blankets; an extensive trade is maintained in lime, gypsum, timber, grain, fruits, wine, wool, cattle and farm implements, and the building of canal boats forms an important industry. The public institutions include the sub-prefecture, tribunals of first instance and of commerce, a communal college and a farm school.
Castelnaudary probably represents the ancient town of Sostomagus, taken during the 5th century by the Visigoths, who, it is conjectured, rebuilt the town, calling it Castrum Novum Arianorum, whence the present name. Early in the 13th century the town was the scene of several struggles during the war against the Albigenses, between Simon IV., count of Montfort, and Raymond VI., count of Toulouse, and their supporters. In 1229 it was deprived of its ramparts, and after these had been rebuilt, it was captured and burned by the Black Prince in 1355, but again rebuilt in 1366. In 1632 it was the scene of a cavalry engagement in which the rebel Henry II., duke of Montmorency, was defeated and captured by the royal troops.