The record for the most Olympic medals won by a single athlete is held by Michael Phelps, an American swimmer. He has achieved a remarkable total of 28 medals throughout his Olympic career, including 23 golds. Phelps' dominance in the water has made him a legendary figure in the world of sports, inspiring many athletes and fans alike. His achievements span over four Olympic Games, showcasing his unparalleled talent, dedication, and versatility in swimming.