O-8 was laid down 27 February 1917 by Fore River Shipbuilding Co., Quincy, Mass.; launched 31 December 1917; sponsored by Mrs. Alice C. Burg; and commissioned 11 July 1918, Lt. Comdr. R.A. Burgin command.
During the final stages of World War I, O-8 operated out of Philadelphia on coastal patrol duty from Cape Cod to Key West. She departed Newport 2 November 1918 with other subs ordered to duty in European waters; the duty was cancelled, however, as the Armistice was signed before the vessels reached the Azores.
The end of the "war to end all wars" did not terminate O-8's Naval career; she now operated in a training capacity at the sub school, New London. In 1924 she sailed for duty in Panama, where she was classified a 2nd line submarine 25 July 1924. Reverting to a 1st liner on 6 June 1928 she sailed from New London in February 1931 to Philadelphia and decommissioned there 27 May.
The imminence of World War II sparked the recall to service. O-8 recommissioned at Philadelphia 28 April 1941. In June she returned to Submarine School, New London to train students there until war's end.
Departing New London 25 August 1945, the ship steamed to Portsmouth, N.H. and decommissioned there 11 September 1945; she was struck from the Navy Register 11 October 1945 and was sold to John J. Duane Co. of Quincy 4 September 1946.