YONNE, a department of central France, formed partly from the province of Champagne proper (with its dependencies, Sénonais and Tonnerrois), partly from Burgundy proper (with its dependencies, the county of Auxerre and Avallonnais) and partly from Gâtinais (Orléanais and Île-de-France). It is bounded by Aube on the N.E., Côte-d'Or on the S.E., Nièvre on the S., Loiret on the W. and Seine-et-Marne on the N.W. Pop. (1906) 315,199. Area, 2880 sq. m. The highest elevation (2000 ft.) is in the granitic highlands of Morvan, in the S.E., where other peaks range from 1300 to 1600 ft. The department belongs to the basin of the Seine, except a small district in the S.W. (Puisaye), which belongs to that of the Loire. The river Yonne flows through it from S. to N.N.W., receiving on the right bank the Cure, the Serein and the Armançon, which water the S.E. of the department. Farther N. it is joined by the Vanne, between which and the Armançon lies the forest-clad plateau of the Pays d'Othe. To the W. of the Yonne, in the Puisaye, are the sources of the Loing, another tributary of the Seine, and of its affluents, the Ouanne and the Lunain. The Yonne is navigable throughout the department, and is connected with the Loire by the canal of Nivernais, which in turn is connected with that of Briare, which connects the Seine and the Loire. The climate is temperate, except in the Morvan, where the extremes of heat and cold are greater, and where the rainfall is most abundant. The prevailing winds are S.W. and W.
The department is essentially agricultural. Wheat and oats are the chief cereals; potatoes, sugar-beet, lucerne, mangoldwurzel and other forage plants are also cultivated, and there is much good pasture.
The vineyards of the Tonnerrois and Auxerrois produce the finest red wines of lower Burgundy, and those of Chablis the finest white. The wine of the Côte St Jacques (Joigny) is also highly esteemed. Cider-apples arc the chief fruit. Charny is a centre for the rearing of horses. Forests cover considerable areas of the department and consist chiefly of oak, beech, hornbeam, elm, ash, birch and pine. Quarry products include building-stone, ochre and cement. Among the industrial establishments are tanneries, tile-works, saw-mills and breweries, but there is little manufacturing activity. Cereals, wines, firewood, charcoal, ochre and bark are exported.
The department is served chiefly by the Paris-Lyon railway. The canal of Burgundy, which follows the valley of the Armançon, has a length of 57 m. in the department, that of Nivernais, following the valley of the Yonne, a length of 33 m. The department constitutes the archiepiscopal diocese of Sens, has its court of appeal in Paris, its educational centre at Dijon, and belongs to the district of the V. army corps. It is divided into five arrondissements (37 cantons, 486 communes), of which the capitals are Auxerre, also capital of the department, Avallon, Sens, Joigny and Tonnerre, which with those of Chablis, St Florentin and Vézelay are its most noteworthy towns and are treated separately. Yonne is rich in objects of antiquarian and architectural interest. At Pontigny there is a Cistercian abbey, where Thomas Becket spent two years of his exile. Its church is an excellent type of the Cistercian architecture of the 12th century. The fine 12th-century château of Druyes, which stands on a hill overlooking the village, once belonged to the counts of Auxerre and Nevers. Villeneuve-sur-Yonne has a medieval keep and gateways and a church of the 13th and 16th centuries. The Renaissance châteaux of Fleurigny, Ancy-le-France and Tanlay, the last-named for some time the property of the Coligny family, and the château of St Fargeau, of the 13th century, rebuilt by Mademoiselle de Montpensier under Louis XIV., are all architecturally remarkable. At St Moré there are remains of the Roman road from Lyons to Gallia Belgica and of a Roman fortified post.