RETHEL, a town of N. France, capital of an arrondissement in the department of Ardennes, on the right bank of the Aisne and the Ardennes canal, 31 m. S.W. of Mézières by rail. Pop. (1906) 5254. The church of St Nicholas was formed by the amalgamation of two churches, the oldest of which dates from the 13th century. Rethel has a sub prefecture, a tribunal of first instance, a board of trade arbitration, a chamber of arts and manufactures and a school of agriculture, and carries on wool-spinning, the weaving of light woollen fabrics, and the manufacture of millboard and farm implements.

Rethel (Castrum Retectum), of Roman origin, was from the end of the 10th century the seat of a countship which passed successively to the families of Flanders, Burgundy, Cleves, Foix and Gonzaga. In 1581 it was erected into a duchy in favour of the latter. In 1663 it was sold by Charles VI. de Gonzaga to Mazarin, whose family held it till the Revolution.