USS Patrol No. 8 (SP-56), often rendered as USS Patrol #8, was an armed motorboat that served in the United States Navy as a patrol vessel from 1917 to 1919. Patrol No. 8 was built as a private motorboat of the same name in 1916 by Murray and Tregurthe at Boston, Massachusetts. The U.S. Navy leased Patrol No. 8 from her owner, millionaire Harold Stirling Vanderbilt of New York City, on 10 May 1917 and commissioned her for service in World War I as USS Patrol No. 8 (SP-56) on 11 May 1917. Coincidentally, at this same time, Vanderbilt, a Naval Reserve officer, was ordered to active duty and given command the Patrol No. 8.