RÉTHÉL, a town of France, capital of an arrondissement in the department of Ardennes, on a steep slope on the right bank of the Aisne, 22 miles S.W. of Mézières. Its broad, straight streets are lined with houses generally ill built, and frequently only of wood. A large market-house, several churches, a theatre, and prisons, are the chief buildings of the town. The principal church is a remarkable building, formed by the union of two placed side by side; and it is decorated with bas-reliefs and other sculptures. Three ancient gates of the town still remain. Réthel has a college, agricultural society, chamber of manufactures, and court of law. It is a busy place, manufacturing leather, woollen cloth, and other articles, in which there is also an active trade. Pop. (1856), 7214.