Basses-Pyrénées, a department of south-western France, at the angle of the Bay of Biscay, formed in 1790, two-thirds of it from Béarn and the rest from three districts of Gascony - Basse-Navarre, Soule and Labourd. The latter constitute the Basque region of France (see Basques) and cover the west of the department. Basses-Pyrénées is bounded N. by Landes and Gers, E. by Hautes-Pyrénées (which has two enclaves forming five communes within this department), S. by Spain, and W. by the Atlantic Ocean. Pop. (1906) 426,817. Area, 2977 sq. m. The whole of the south of the department is occupied by the western and lower summits of the Pyrenees. The remainder consists of a region of heaths and plateaus to the northeast of the Gave de Pau, and of hills divided by numberless fertile valleys to the west of that river. The height of the mountains of the southern frontier increases gradually from west to east. The peak of the Rhune, to the south of St Jean de Luz, rises only to 2950 ft.; and on the border of the Basque country the mean height of the summits is not much greater. The peak of Orhy alone, in the south of the valley of Mauléon, reaches 6618 ft.
But beyond that of Anie (8215 ft.), on the meridian of Orthez, which marks the boundary of Béarn, much loftier elevations appear, - Mourrous (9760 ft.), on the border of Hautes-Pyrénées, and the southern peak of Ossau (9465 ft.). The frontier between France and Spain, for the most part, follows the crest-line of the main range. Forts guard the upper valleys of the Nive and the Aspe, along which run important passes into Spain. The general direction of the rivers of the department is towards the north-west. The streams almost all meet in the Adour through the Gave de Pau, the Bidouze, and the Nive. In the north-east the two Luys flow directly to the Adour, which they join in Landes. In the south-west the Nivelle and the Bidassoa flow directly into the sea. The lower course of the Adour forms the boundary between Basses-Pyrénées and Landes; it enters the sea a short distance below Bayonne over a shifting bar, which has often altered the position of its mouth. The Gave de Pau, a larger stream than the Adour, passes Pau and Orthez, but its current is so swift that it is only navigable for a few miles above its junction with the Adour. On the left it receives the Gave d'Oloron, formed by the Gave d'Ossau, descending from the Pic du Midi, and the Gave d'Aspe, which rises in Spain. An important affluent of the Gave d'Oloron, the Saison or Gave de Mauléon, descends from the Pic d'Orhy. From the Pic des Escaliers, which rises above the forest of Iraty, the Bidouze descends northwards; while the forest, though situated on the southern slope of the chain, forms a part of French territory.
The Nive, a beautiful river of the Basque country, takes its rise in Spain; after flowing past St Jean-Pied-de-Port, formerly capital of French Navarre and fortified by Vauban to guard the pass of Roncevaux, it joins the Adour at Bayonne. The Nivelle also belongs only partly to France and ends its course at St Jean-de-Luz. The Bidassoa, which is only important as forming part of the frontier, contains the Ile des Faisans, where the treaty of the Pyrenees was concluded (1659), and debouches between Hendaye (France) and Fuenterrabia (Spain).
The climate of the department is mild and it has an abundant rainfall, partly due to the west wind which drives the clouds from the gulf of Gascony. The spring is rainy; the best seasons are summer and autumn, the heat of summer being moderated by the sea. The winters are mild. The air of Pau agrees with invalids and delicate constitutions, and St Jean-de-Luz and Biarritz are much frequented by winter visitors.
Despite extensive tracts of uncultivated land, the department is mainly agricultural. Maize and wheat are the chief cereals; potatoes, flax and vegetables are also produced. Pasture is abundant, and horses, cattle, sheep and pigs are largely reared. The vine is grown on the lower slopes sheltered from the north wind, the wines of Jurançon, near Pau, being the most renowned. Of the fruits grown, chestnuts, cider-apples, and pears are most important. About one-thirteenth of the department consists of woods, a very small proportion of which belong to the government, the rest to the communes and private individuals.
The department furnishes salt, building-stone, and other quarry products. There are mineral springs at Eaux-Bonnes, Eaux-Chaudes, Cambo-les-Bains (resorted to by the Basques on St John's Eve), St Christau, and Salies. At Le Boucau, 3 m. from Bayonne, there are large metallurgical works, the Forges de l'Adour, and chemical works. The manufactures of the department include woollen caps and sashes, cord slippers, chocolate, and paper, and there are also tanneries, saw- and flour-mills. "Bayonne hams" and other table delicacies are prepared at Orthez. There is a considerable fishing population at Bayonne and St Jean-de-Luz. Bayonne is the principal port. Exports consist chiefly of timber, mine-props, minerals, wine, salt and resinous products. Coal, minerals, phosphates, grain and wool are leading imports. The interior commerce of the department is, however, of greater importance to its inhabitants; it takes the form of exchange of products between the regions of mountain and plain. The railway lines of Basses-Pyrénées, the chief of which is that from Bayonne to Toulouse via Orthez and Pau, belong to the Southern Company. The Adour, the Nive and the Bidouze are navigable on their lower courses.
The department has five arrondissements - Pau, Bayonne, Oloron, Orthez and Mauléon, divided into 41 cantons and 559 communes. It constitutes the diocese of Bayonne, comes within the educational circumscription (académie) of Bordeaux and belongs to the district of the XVIII. army corps. Pau, the capital and seat of a court of appeal, Bayonne, Oloron, Biarritz, Orthez, Eaux-Bonnes, and St Jean-de-Luz are the principal towns. The following places are also of interest: - Lescar, which has a church of the 12th and 16th century, once a cathedral; Montaner, with a stronghold built in 1380 by Gaston Phoebus, count of Foix and viscount, of Béarn; and Sauveterre, a town finely situated on the Gave d'Oloron, with an old bridge, remains of a feudal castle, and a church in the Romanesque and Gothic styles.