Aveyron, a department of southern France, bounded N. by Cantal, E. by Lozère and Card, S.W. by Tarn and W. by Tarn-et-Garonne and Lot. Area, 3386 sq. m. Pop. (1906) 377,299. It corresponds nearly to the old district of Rouergue, which gave its name to a countship established early in the 9th century, and united with that of Toulouse towards the end of the 11th century. The earliest known natives of this region were the Celtic Rutheni, to whom the numerous megalithic monuments found in the department are attributed. Aveyron lies on the southern border of the central plateau of France. Its chief rivers are the Lot in the north, the Aveyron in the centre and the Tarn in the south, all tributaries of the Garonne. They flow from east to west, following the general slope of the department, and divide it into four zones. In the north-east, between the Lot and its tributary the Truyère, lies the lonely pastoral plateau of the Viadène, dominated by the volcanic mountains of Aubrac, which form the north-eastern limit of the department and include its highest summit (4760 ft.). Entraygues, at the confluence of the Lot and the Truyère, is one of the many picturesque towns of the department.

Between the Lot and the Aveyron is a belt of causses or monotonous limestone table-lands, broken here and there by profound and beautiful gorges - a type of scenery characteristic of Aveyron. This zone is also watered by the Dourdou du Nord, a tributary of the Lot. The salient feature of the region between the Tarn and the Aveyron is the plateau of the Ségala, bordered on the east by the heights of Lévezou and Palanges and traversed from east to west by the deep valley of the Viaur, a tributary of the Aveyron. The country south of the Tarn is occupied in great part by the huge plateau of Larzac, which lies between the Causse Noir and the Causse St Affrique, the three forming the south-western termination of the Cévennes. On the Causse Noir is found the fantastic chaos of rocks and precipices known as Montpellier-le-Vieux, resembling the ruins of a huge city. The climate of Aveyron varies from extreme rigour in the mountains to mildness in the sheltered valleys; the south wind is sometimes of great violence. Wheat, rye and oats are the chief cereals cultivated, the soil of Aveyron being naturally poor. Other crops are potatoes, colza, hemp and flax.

The mainstay of the agriculture of the department is the raising of live-stock, especially of cattle of the Aubrac breed, for which Laguiole is an important market. The wines of Entraygues, St Georges, Bouillac and Najac have some reputation; in the Ségala chestnuts form an important element in the food of the peasants, and the walnut, cider-apple, mulberry (for the silk-worm industry), and plum are among the fruit trees grown. The production of Roquefort cheeses is prominent among the agricultural industries. They are made from the milk of the large flocks of the plateau of Larzac, and the choicest are ripened in the even temperature of the caves in the cliff which overhangs Roquefort. The minerals found in the department include the coal of the basins of Aubin and Rodez as well as iron, zinc and lead. Quarries of various kinds of stone are also worked. The chief industrial centres are Decazeville, which has metallurgical works, and Millau, where leather-dressing and the manufacture of gloves have attained considerable importance.

Wool-weaving and the manufacture of woollen goods, machinery, chemicals and bricks are among the other industries.

There are five arrondissements, of which the chief towns are Rodez, capital of the department, Espalion, Millau, St Affrique and Villefranche, with 43 cantons and 304 communes. Rodez is the seat of a bishopric, the diocese of which comprises the department. Aveyron belongs to the 16th military region, and to the académie or educational circumscription of Toulouse. Its court of appeal is at Montpellier. The department is traversed by the lines both of the Orléans and Southern railways. The more important towns are Rodez, Millau, St Affrique, Villefranche-de-Rouergue and Decazeville. The following are also of interest: - Sauveterre, founded in 1281, a striking example of the bastide (q.v.) of that period; Conques, which has a remarkable abbey-church of the 11th century like St Sernin of Toulouse in plan and possessing a rich treasury of reliquaries, etc.; Espalion, where amongst other old buildings there are the remains of a feudal stronghold and a church of the Romanesque period; Najac, which has the ruins of a magnificent château of the 13th century; and Sylvanès, with a church of the 12th century, once attached to a Cistercian abbey.