USS O-2 (SS-63) was one of 16 O-class submarines built for the United States Navy during World War I.

The O-class submarines were designed to meet a Navy requirement for coastal defense boats.

[2] For surface running, the boats were powered by two 440-brake-horsepower (328 kW) diesel engines, each driving one propeller shaft.

With increasing possibility of U.S. involvement in World War II, O-2 recommissioned at Philadelphia on 3 February 1941.

This article incorporates text from the public domain Dictionary of American Naval Fighting Ships.