USS St. Mary's (SP-1457)

The third USS St. Mary's (SP-1288), also spelled St. Marys, was a United States Navy patrol vessel in service from 1917 to 1918.

St. Mary's was built as a civilian motorboat of the same name in 1912 by Ruark at Hooper's Island, Maryland. On 17 August 1917, the U.S. Navy acquired her from her owner, the Maryland Conservation Commission, for use as a section patrol boat during World War I. She was placed in service as USS St. Mary's or St. Marys (SP-1457) on 17 October 1917.

Assigned to the Baltimore Section of the 5th Naval District, St. Mary's served on patrol duties on the Chesapeake Bay and on the Potomac River between Point Lookout, Maryland, and the mouth of Maryland's St. Mary's River for the rest of World War I and for two weeks after it ended, concluding her final patrol on 25 November 1918.

The Navy placed St. Mary's out of service on 26 November 1918 and returned her to the Conservation Commission the same day.