Gary J. Dilley (born January 15, 1945) is an American former competition swimmer and Olympic medalist. He represented the United States at the 1964 Summer Olympics in Tokyo, where he received a silver medal in men's 200-meter backstroke, finishing second behind American teammate Jed Graef. Dilley set new Olympic records in the heats and semifinals, but Graef improved upon Dilley's records in the event's second semifinal and final. Dilley attended Michigan State University, where he swam for the Michigan State Spartans swimming and diving team under Head Coach Charles McCaffree. Dilley graduated from the Indiana University School of Dentistry, went on to earn a doctorate in orthodontics from the University of North Carolina School of Dentistry and then specialized in pediatric dentistry and orthodontics. He maintained his orthodontic practice in Cary, North Carolina, and was formerly a faculty member at the UNC School of Dentistry.