United States Battleship Division Nine was a division of four, later five, dreadnought battleships of the United States Navy's Atlantic Fleet that constituted the American contribution to the British Grand Fleet during World War I. Although the U.S. entered the war on 6 April 1917, hesitation among senior officers of the U.S. Navy as to the wisdom of dividing the American battle fleet prevented the immediate dispatch of any capital ships for service in the war zone. Following a direct request from the British Admiralty and a series of high level staff meetings, American opinion changed, and Battleship Division Nine joined the Grand Fleet on 7 December 1917. Within that organization, the Division served as the Sixth Battle Squadron.
While serving with the Grand Fleet, Battleship Division Nine was forced to adapt quickly to unfamiliar British methods and standards. New signals and maneuvers were adopted relatively smoothly, while more stringent gunnery standards proved more difficult to achieve. On a personal level, relations between American and British officers and men were notably cordial.