_off_the_Mare_Island_Naval_Shipyard,_California_(USA),_on_14_July_1943_(19-N-48937).jpg)
A fleet submarine is a submarine with the speed, range, and endurance to operate as part of a navy's battle fleet. Examples of fleet submarines are the British First World War era K class and the American World War II era Gato class.
The term has survived in Britain to refer to modern nuclear-powered attack submarines. In the United States Navy, the term came to be used primarily for the long-range submarines that served in World War II.