USS John S. McCain (DDG-56) is an Arleigh Burke-class destroyer currently in the service of the United States Navy. She is part of the Destroyer Squadron 23 within the Third Fleet, and has her homeport at Naval Station Everett in Everett, Washington.

Destroyer Squadron 23 is a squadron of United States Navy destroyers based out of San Diego, California. The squadron is best known for its actions during World War II, most notably the Battle of Cape St. George, under the command of then-Commodore Arleigh Burke. Currently, the DESRON is assigned to Carrier Strike Group Nine, which includes USS Theodore Roosevelt (CVN-71), USS Chosin (CG-65), USS Lake Erie (CG-70), and Carrier Air Wing Eleven.