California, Gulf of, an arm of the Pacific Ocean jutting into northwestern Mexico between the Lower California peninsula and the mainland. It is sometimes called the Sea of Cortez. The gulf is about 700 miles (1, 100 km) long and 60 to 130 miles (100 to 210 km) wide. It is shallow in the north, where the silt-laden waters of the Colorado River enter it, but reaches depths of more than 9,000 feet (2,700 m) in the south. Tiburón and Ángel de la Guarda are the largest islands. Most of the coastal area bordering the gulf is dry, desolate, sparsely settled land.

La Paz, on the peninsula, and Guaymas, on the east coast, are the largest cities and main ports. An abundance of seafood is obtained from the gulf. Deep-sea sportfishing is a main attraction of resorts located in several areas along the coast.