Ebro (ancient Iberus or Hiberus), river, northeastern Spain, rising in the Cantabrian Mountains, and emptying into the Mediterranean Sea after a southeastern course of 910 km (565 mi). The Ebro is the only major river of Spain that flows into the Mediterranean. Its principal tributaries are the Ega, Aragón, Arba, Gállego, and Segre, from the north, and the Jalón, Huerva, Aguasvivas, Martín, Guadalope, and Matarraña, from the south. The Ebro is important to irrigation and drains an area of almost 82,880 sq km (almost 32,000 sq mi). Oceangoing vessels can ascend the river only to the city of Tortosa.

During the Spanish Civil War (1936-39), the Ebro was of tactical importance to the Republican government. Late in July 1938, Spanish Loyalists started an offensive alongside the river that halted the progress of the army of General Francisco Franco for the rest of the year.