USS Chicago (SSN-721) is a Los Angeles-class submarine, the fourth ship of the United States Navy to be named for the city of Chicago, Illinois. The contract to build her was awarded to Newport News Shipbuilding and Dry Dock Company in Newport News, Virginia on 13 August 1981 and her keel was laid down on 5 January 1983. She was launched on 13 October 1984 sponsored by Mrs. Vicki Ann Paisley, wife of Melvyn R. Paisley assistant Secretary of the Navy, and commissioned on 27 September 1986. The Chicago was retired in 2023.

The Los Angeles class of submarines are nuclear-powered fast attack submarines (SSN) in service with the United States Navy. Also known as the 688 class after the hull number of lead vessel USS Los Angeles (SSN-688), 62 were built from 1972 to 1996, the latter 23 to an improved 688i standard. As of 2024, 24 of the Los Angeles class remain in commission—more than any other class in the world—and they account for almost half of the U.S. Navy's 50 fast attack submarines.