Garonne (ane. Gurumna), a river of S. France, which derives its name from its two head streams, the Gar, which rises in the Spanish valley of Aran, and the Onne, which descends from the glaciers of A6 in the Pyrenees. Flowing N. W., it enters France at a place called Pont-du-Roi, in the department of Haute-Garonne. It runs thence N. E. to Toulouse, whence it flows generally N. W. It passes the towns of St. Beat, Montrejeau, St. Martory, Cazeres (where it becomes navigable), Carbonne, Muret, Toulouse, Verdun, Agen, Marmande, and Bordeaux, a few miles below which it is joined by the Dordogne and forms the estuary or river known as the Gi-ronde. Its chief affluents on the right bank are the Ariege, Tarn, and Lot; on the left, the Save, Gimone, Gers, Baise, and Ciron. Its length, including the Gironde, is about 360 m., of which 260 are navigable; but including its feeders, which communicate with 12 departments, the total river navigation of its basin is about 1,000 m. Large vessels ascend to Bordeaux, where it forms a large basin. At Toulouse it is joined by the canal du Midi, by means of which and by this river the Mediterranean is connected with the bay of Biscay. The basin of the Garonne includes a tract of country about 185 m. in average length and breadth.

The upper part of its course lies through narrow defiles and is much obstructed; from Toulouse it is broad but shallow, and navigation is more or less impeded by the debris which it brings down as far as Marmande, about 50 m. above Bordeaux. Its banks are fertile and picturesque.