John Kelly was born on July 8, 1928, in Youngstown, Ohio. He enlisted in the U.S. Marine Corps on August 9, 1951, and completed basic training at MCRD Parris Island, South Carolina, in October 1951. PFC Kelly next attended Infantry training at Camp Pendleton, California, from November 1951 to January 1952, and he then deployed to Korea in February 1952. He arrived in Korea and joined C Company, 1st Battalion, 7th Marine Regiment of the 1st Marine Division in March 1952, and was Killed in Action on May 28, 1952, during a battle for which he would later be posthumously awarded the Medal of Honor. John Kelly was buried at Jefferson Memorial Cemetery in Pittsburgh, Pennsylvania. His Medal of Honor was presented to his mother by Vice President Richard M. Nixon on September 9, 1953.

His Medal of Honor Citation reads:

For conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty while serving as a radio operator of Company C, in action against enemy aggressor forces. With his platoon pinned down by a numerically superior enemy force employing intense mortar, artillery, small-arms, and grenade fire, Pfc. Kelly requested permission to leave his radio in the care of another man and to participate in an assault on enemy key positions. Fearlessly charging forward in the face of a murderous hail of machine-gun fire and hand grenades, he initiated a daring attack against a hostile strongpoint and personally neutralized the position, killing two of the enemy. Unyielding in the face of heavy odds, he continued forward and singlehandedly assaulted a machine-gun bunker. Although painfully wounded, he bravely charged the bunker and destroyed it, killing three of the enemy. Courageously continuing his one-man assault, he again stormed forward in a valiant attempt to wipe out a third bunker and boldly delivered point-blank fire into the aperture of the hostile emplacement. Mortally wounded by enemy fire while carrying out this heroic action, Pfc. Kelly, by his great personal valor and aggressive fighting spirit, inspired his comrades to sweep on, overrun and secure the objective. His extraordinary heroism in the face of almost certain death reflects the highest credit upon himself and enhances the finest traditions of the U.S. Naval Service. He gallantly gave his life for his country.