The California Sea Lion (Zalophus californianus) is an aquatic marine (saltwater) mammal in the Pinnipedia Clade and Otariidae family of sea lions and fur seals. It is an otariid or otary – a seal with external ear flaps – and a pinniped – fin footed. 

The California Sea Lion has light to brown or black fur, although the female can have light grey or silver fur after moulting. It does not have a mane of hair on its back, like other sea lions. It has a sleek, slender build with a thick neck, broad chest, broad shoulders, and a long, protruding face and nose. It has white whiskers on its chin called vibrissae. It has small external ears on the sides of its face. 

It has flippers for swimming. Its movement in water is called aquatic locomotion. Its body is streamlined with oily fur for swimming fast underwater. It has a flexible spine (backbone). On land, it walks on its foreflippers (front flippers). Its fatty body, which keeps it warm and buoyant, is called blubber.