Ebro, a river of Spain, the Iberus of the Romans, which gave the name of Iberia to the country it waters. It rises in the mountains on the N. border of Spain, in the province of San-tander, and flows S. E. at first between lofty and picturesque heights, separating Alava and Navarre from Old Castile, intersecting Aragon near its centre, and after a course of about 400 m. emptying into the Mediterranean through a double embouchure at Cape Tortosa, near the S. extremity of Catalonia, in lat. 40° 42' N. At Mequinenza it passes through a defile where once was probably a barrier restraining its waters as a lake in the country of Aragon. Its principal tributaries are the Aragon, Gallego, and Segre, on the left or N. side, and the Oca, Jalon, and Guadalupe, on the right or S. It abounds with shoals and rapids, but boats may pass with difficulty as high as Tudela in Navarre. A canal has been cut parallel with its bank from Tudela to Sastago, about 40 m. below Saragossa. Improvements have also been made in the bed of the river lower down, and from a point near Amposta the San Carlos canal has been opened southerly across the delta to the harbor of Los Alfaques. The principal traffic is the transport of grain, and the floating of timber from the northern forests.

The Ebro was the boundary between the possessions of Rome and Carthage, and afterward between those of Charlemagne and the Moors.