USS Growler (SSG-577) was an early attempt by the U.S. Navy to field a cruise missile submarine that would provide a nuclear deterrent using its second series of cruise missiles. Built to deliver the Regulus I cruise missile, Growler was the second and final submarine of the Grayback class, fourth ship of the United States Navy to be named after the growler. Since Regulus I and Regulus II programs had problems, Growler and Grayback were the only two submarines built in this class as instead, the U.S. Navy veered its nuclear deterrence efforts into submarine launched ballistic missiles (SLBMs)—the Polaris missile program.

The SSM-N-8A Regulus or the Regulus I was a United States Navy-developed ship-and-submarine-launched, nuclear-capable turbojet-powered second generation cruise missile, deployed from 1955 to 1964. Its development was an outgrowth of U.S. Navy tests conducted with the German V-1 missile at Naval Air Station Point Mugu in California. Its barrel-shaped fuselage resembled that of numerous fighter aircraft designs of the era, but without a cockpit. Test articles of the Regulus were equipped with landing gear and could take off and land like an airplane. When the missiles were deployed they were launched from a rail launcher, and equipped with a pair of Aerojet JATO bottles on the aft end of the fuselage.