an arrondissement in the department of the Orne, in the N.W. of France, comprehending an extent of 416 square miles, or 266,240 English acres. It is divided into six cantons, with 72,418 inhabitants. The capital on the river Sarthe bears the same name. It is well built, and contains a cathedral, a church of the 8th century, a courthouse, and a theatre. It was the ancient seat of the counts and dukes of Alençon. Its manufactures include tanning, spinning, bleaching, printing calicoes, and lace-making.

Pop. 13,533.