Shatt-al-Arab

Waterway formed by the confluence of the rivers Euphrates and Tigris; length 190 km/120 mi to the Gulf. Basra, Khorramshahr, and Abadan stand on it. Its main tributary is the Karun River.

Its lower reaches form a border of disputed demarcation between Iran and Iraq. In 1975 the two countries agreed on the deepest water line as the frontier, but Iraq repudiated this in 1980. This dispute was a factor in the Iran–Iraq war from 1980–88, and the waterway was the subject of long and bitter fighting after Iraq invaded and claimed both banks.