USS Moccasin (SS-5) (later renamed A-4) was one of seven Plunger-class submarines built for the United States Navy (USN) in the first decade of the 20th century.

[1] Moccasin was laid down under the direction of Arthur Leopold Busch on 8 November 1900 in Elizabeth, New Jersey at the Crescent Shipyard, launched on 20 August 1901, and commissioned on 17 January 1903 at the Holland Torpedo Boat Station at New Suffolk, N.Y.

The submarine ran aground in North Carolina's outer banks in late 1903, and was several miles away from the Wright Brothers' inaugural flight on 17 December 1903.

Recommissioned on 10 February 1910, she was assigned to the First Submarine Division, Asiatic Torpedo Fleet, based in the Manila area.

During World War I, like her sister-ships, she patrolled the entrance to Manila Bay and convoyed ships moving out of local waters.