The California Sea Lion (Zalophus californianus californianus) is a coastal sea lion of the eastern Pacific often associated with marinas and wharves. Males grow to 340 kg (750 pounds) and 2.4 m (8 feet) long, females are generally no larger than 100 kg (220 pounds). Males grow a large crest of bone on the top of their heads as they reach sexual maturity, and it is this that gives the animal its generic name (loph is "forehead" and za- is an emphatic; Zalophus californianus means "Californian Big-head").

California Sea Lions are intelligent and adaptable, and are often trained as entertainers at ocean parks and zoos as well as by researchers studying interspecies cooperation in the marine environment.

There are three subspecies: Zalophus californianus californianus is the nominate race, the others are the Galapagos Sea Lion (Z. c. wollenbacki) and the Japanese Sea Lion (Z. c. japonicus) which is now believed to be extinct.

Sea lions on platforms near Pier 39 in San Francisco, California

Sea lions in Newport, Oregon