51/DD-51) was the lead ship of O'Brien-class destroyers built for the United States Navy prior to the American entry into World War I.

The ship was the second US Navy vessel named in honor of Jeremiah O'Brien and his five brothers Gideon, John, William, Dennis, and Joseph who, together on the sloop Unity, captured a British warship during the American Revolutionary War.

After returning to the United States in January 1919, O'Brien revisited European waters in May to serve as one of the picket ships for the NC-type seaplanes in the first aerial crossing of the Atlantic.

The General Board of the United States Navy had called for two anti-aircraft guns for the O'Brien-class ships, as well as provisions for laying up to 36 floating mines.

O'Brien was commissioned into the United States Navy on 22 May 1915 after which she conducted her shakedown cruise between Newport, Rhode Island, and Hampton Roads, Virginia.

At 05:30 on 8 October 1916, wireless reports came in of a German submarine stopping ships near the Lightship Nantucket, off the eastern end of Long Island.

After an SOS from the British steamer SS West Point was received at about 12:30, Rear Admiral Albert Gleaves ordered O'Brien and other destroyers at Newport to attend to survivors.

After fitting out at Brooklyn Navy Yard, she got underway from New York on 15 May with Cummings,[1][17] Nicholson,[18] Cushing,[19] and Sampson,[20] and joined convoy at Halifax, Nova Scotia, en route to Ireland.

She patrolled off the Irish coast in company with other destroyers answering distress calls and meeting eastbound convoys to escort them through the war zone.

[1] After the signing of the Armistice on 11 November, which ended all fighting, O'Brien transported mail and passengers between Brest, France, and Plymouth, England.

[1] The ship was struck from the Naval Vessel Register on 8 March 1935,[5] and broken up at the Philadelphia Navy Yard, and her materials sold for scrap on 23 April.