The Gato class of submarines were built for the United States Navy and launched in 1941–1943. Named after the lead ship of the class, USS Gato, they were the first mass-production U.S. submarine class of World War II.

A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as boats rather than ships irrespective of their size.