LYONS, Gulf of (the ancient Gallicus Sinus), an extensive bay of the Mediterranean Sea, formed by the southern coast of France, between the Pyrenean range on the W., and a headland near Toulon on the E. It extends 145 miles from one extremity to the other, and washes the shores of the six departments of Pyrenees-Orientales, Aude, Herault, Bouches-du-Rhône, and part of Var. The principal rivers that enter it are,—the Rhône, the Aude, and Têt; and the chief towns on its coast-line are,—Marseille, Cette, and Port Vendres. Its shores in many parts are broken by long lagoons and low islands.