a town of France, capital of an arrondissement in the department of Seine-et-Oise, on the side of a steep hill on the right bank of the Oise, 18 miles N.W. of Paris. The river is here crossed by a bridge, whence the town derives its name (Pont Oise, Oise bridge). Remains of the castle and walls that formerly defended the town still exist. The streets are in general steep and narrow. There is an interesting church in various styles of architecture; a Gothic court-house, a public library, and a splendid hospital. Pontoise has also a college and several schools. Clocks and watches, chemical substances, cotton yarn, leather, &c., are manufactured here; and there are many corn-mills turned by the Oise and its affluent the Vienne. Pop. (1856) 5366.