Kelly was a male Human Starfleet officer who lived during the mid-23rd century. He served in the command division aboard the USS Enterprise under Captain James T. Kirk, during a historic five-year mission that starship undertook. He served as one of the ship's security guards in 2267.
That year, Kelly served on a security team ordered by Lieutenant Commander Giotto to hunt for the Horta on Janus VI. He was scouting alone when the mother Horta attacked him. By the time help arrived, he had been completely dissolved by acid. (TOS: "The Devil in the Dark")