Senlis, a town of northern France, in the department of Oise, on the right side of the Nonette, a left-hand affluent of the Oise, 34 m. N.N.E. of Paris by the Northern railway on the branch line (Chantilly-Crepy) connecting the Paris-Creil and Paris-Soissons lines. Pop. (1906) 6074. Its antiquity, its historical monuments and its situation in a beautiful valley, in the midst of the three great forests of Hallatte, Chantilly and Ermenonville, render it interesting. Its Gallo-Roman walls, 23 ft. high and 13 ft. thick, are, with those of St Lizier (Ariege) and Bourges, the most perfect in France. They enclose an oval area 1024 ft. long from E. to W. and 794 ft. wide from N. to S. At each of the angles formed by the broken lines of which the circuit of 2756 ft. is composed stands or stood a tower; numbering originally twenty-eight, and now only sixteen, they are semicircular in plan, and up to the height of the wall are unpierced. The Roman city had only two gates; the present number is five. The site of the praetorium was afterwards occupied by a castle occasionally inhabited by the kings of France from Clovis to Henry IV., and still represented by ruins dating from the i rth, 13th and 16th centuries. In the neighbourhood of Senlis the foundations of a Roman amphitheatre have also been discovered. The old cathedral of Notre Dame (12th, r3th and 16th centuries) was begun in 1155 on a vast scale; but owing to the limited resources of the diocese progress was slow and the transept was finished only under Francis I. The total length is 312 ft. (outside measurement), but the nave (92 ft. high) is shorter than the choir. At the west front there are three doorways and two bell towers. The right-hand tower (256 ft. high) is very striking: it consists, above the belfry stage, of a very slender octagonal drum with open-work turrets and a spire with eight dormer windows. The left-hand tower, altered in the 16th century, is crowned by a balustrade and a sharp roof. In the side portals, especially in the southern, the flamboyant Gothic is displayed in all its delicacy. Externally the choir is extremely simple. In the interior the sacristy pillars with capitals of the 10th century are noteworthy. The episcopal palace, now an archaeological museum, dates from the 13th century; the old collegiate church of St Frambourg was built in the 12th century in the style which became characteristic of the "saintes chapelles" of the r3th and 14th centuries; St Pierre (chiefly of the 15th and 16th centuries) serves as a market. The ecclesiastical college of St Vincent, occupying the old abbey of this name, has an interesting church probably of the 12th century. Its date has, however, been greatly disputed by archaeologists, who sometimes wrongly refer it to Queen Anne of Russia, foundress in the 11th century of the abbey. The town hall (15th century) and several private houses are also of architectural interest.
Senlis has tribunals of first instance and of commerce and a sub-prefecture. The manufacture of bricks and tiles, cardboard, measures and other wares are among the industries. The town is an agricultural market.
Senlis can be traced back to the Gallo-Roman township of the Silvanectes, which afterwards became Augustomagus. Christianity was introduced by St Rieul probably about the close of the 3rd century. During the first two dynasties of France Senlis was a royal residence and generally formed part of the royal domain; it obtained a communal charter in 1173. In the middle ages local manufactures, especially that of cloth, were active. The burgesses took part in the Jacquerie of the 14th century, then sided with the Burgundians and the English; whom, however, they afterwards expelled. The Leaguers were there beaten in 1589 by Henry I., duke of Longueville, and Francois de La Noue. The bishopric was suppressed at the Revolution, and this suppression was confirmed by the Concordat. Treaties between Louis XI. and Francis II., duke of Brittany (1475), and between Charles VIII. and Maximilian of Austria (1493) were signed at Senlis.