town and port, northwestern Algeria, at the western end of the Gulf of Oran. The town was an Almohad naval arsenal in the 12th century. It was under the rulers of Tlemcen in the 15th century and fell to corsairs in 1492. The town was later contested by the Spanish, Portuguese, and Turks until France gained control of it in 1830.

Mers el-Kebir (Arabic: “Great Harbour”) was developed in 1939–56 as a major French naval base. In 1940 most of the French fleet at anchor there was destroyed by British warships to thwart a German takeover of them. Under the terms of the Evian Agreements for Algerian independence in 1962, France was to retain the port for 15 years. Control was relinquished to Algeria, however, in 1968.

Mers el-Kebir lies at the foot of Mount Santon, whose eastern projection forms Mers el-Kebir Point. The port's natural harbour is sheltered from east winds and protected by breakwaters. Pop. (latest est.) 11,002.