Euphrates (Turk. Frat), the largest river of western Asia. It rises from two chief sources in the Armenian mountains; one of them at Dumly, 25 m. N. E. of Erzerum, the other on the northern slope of the Ala Dagh, near the village of Diyadin, and not far from Mt. Ararat. The former, or Northern Euphrates, has the name of Frat from the first, but is known also as the Kara-su (Black river); the latter, or Southern Euphrates, is not called the Frat, but the Murad Chai, though in reality the main river. Both branches flow mainly W. S. W. and meet at Kieban-Maaden, about lat. 38° 50' N. and Ion. 38° 40' E., after a course of respectively 270 and 400 m. The combined stream is here 360 ft. wide, rapid, and very deep. It flows a winding course, mostly S. and S. W., traversing a chain of Mt. Taurus, till it reaches the vicinity of Nizib, where it is deflected S. E., keeps its way without deviation till near its junction with the Tigris, and the united rivers fall, under the name Shat-el-Arab, into the Persian gulf. Its total length is about 1,800 m., its average breadth about 200 yards, and its depth from 12 to 30 ft.

The upper part of its course lies amid lofty mountains, and near the village of Pashtash it plunges through a gorge formed by precipices more than 1,000 ft. in height, and so narrow that it is bridged at the top. It then enters the plains of western and southern Mesopotamia, where the swiftness of its current is diminished, and where in ancient times numerous canals extended from its banks to irrigate the neighboring country. It extricates itself from the marshes of Lemlun just before reaching Korna, the point of its union with the Tigris. It is navigable both below and above the cataracts which it forms in the passes of the Taurus, though numerous islands, shallows, and rapids make its navigation in many places difficult. Its waters are subject to periodical increase from the melting of the snow on the mountains along the upper part of its course, and its inundations were anciently of great advantage to the agriculture of the level districts through which it passes. Under the misrule of the Turks, however, the canals and embankments which regulated the inundations have been neglected. - The Euphrates is linked with the most important events in ancient history. It is mentioned in the Bible as one of the four rivers of the garden of Eden, and is often named the great river.

On its banks stood the city of Babylon, which was for ages not only the capital of great empires, but also one of the greatest commercial emporiums of the world. Indian and Egyptian merchandise destined for Babylon was transshipped in the port of Gerrha, now Katif, in the Persian gulf, from the largo vessels that had made the sea voyage into smaller ones fit for the navigation of the river. Nebuchadnezzar, however, had locks constructed, and dikes raised to contain the waters of the Shat-el-Arab, which allowed vessels of heavy burden to ascend the Euphrates as far as Babylon. It was for a long time the western boundary of the Parthian and the eastern boundary of the I Roman empire. The army of Necho was defeated on its banks by Nebuchadnezzar at Circesium (Carchemish); Cyrus the Younger and Crassus perished after crossing it, the one at Cunaxa, the other at Carrhae; Alexander crossed it at Thapsacus; Trajan and Severus descended it in fleets built in upper Mesopotamia. In recent times the English have tried to use it as their path of communication with India. For this purpose an expedition was sent from England under command of Col. Chesney, which in 1836 descended the river from Bir and surveyed 509 m. of its course.

The steam navigation of the Euphrates, from its mouth to Bir, has since become of some importance. The electric telegraph line from Bagdad to the Persian gulf, which was opened in 1865, skirts the Euphrates as well as the Tigris. It is a singular fact concerning the Euphrates that several thousand years ago the waters do not seem to have reached the sea at all, but were lost in marshes or consumed by irrigation, which was practised on an immense scale under the Babylonian and Assyrian sovereigns. It is certain that at a much later period the Tigris and Euphrates flowed into the sea by distinct channels. Their junction is supposed to have taken place more than 2,000 years ago.