USS Plymouth (PG-57), a patrol gunboat, was the fourth ship of the United States Navy to be named for Plymouth, Massachusetts, a town founded by the Pilgrims in 1620 on Plymouth Bay, about 35 miles southeast of Boston.
Plymouth's keel was laid down in 1931 by the Friedrich Krupp Germaniawerft in Kiel, Germany, as Alva. She was given to the United States Navy on 4 November 1941 by her owner, W. K. Vanderbilt II of New York City, and was placed in reduced commission at Jacksonville, Florida, on 29 December 1941 with Commander F. W. Schmidt in command.