The Kārun (also spelled as Karoun) (Persian: کارون) is Iran's most effluent and only navigable river. It is 450 miles (720 km) long. It rises in the Zard Kuh mountains of the Bakhtiari district in the Zagros Range, receiving many tributaries, such as the Dez and the Kuhrang, before passing through the capital of the Khuzestan Province of Iran, the city of Ahvaz.
The Karun continues toward the Persian Gulf, forking into two primary branches on its delta - the Bahmanshir and the ...see more Haffar - that join the Shatt al-Arab (Arvand Rud in Persian), emptying into the Persian Gulf. The important Island of Abadan is located between these two branches of the Karun. The port city of Khorramshahr is divided from the Island of Abadan by the Haffar branch.
Juris Zarins and other scholars have identified the Karun as one of the four rivers of Eden, the others being the Tigris, the Euphrates and either the Wadi Batin or the Karkheh.