Jim Ryun is a former American middle-distance runner known for his remarkable achievements in track and field during the 1960s. He gained fame as a high school athlete, setting multiple records, and later became an Olympic competitor, representing the United States in the 1964 Tokyo Olympics and the 1968 Mexico City Olympics. Ryun was the first high school athlete to run a mile in under four minutes, achieving this milestone in 1965. He also set world records in the mile and 1500 meters, solidifying his status as one of the greatest runners in history.