Definition of Ryun, Jim
- (1947-), US athlete and politician; full name James Ronald Ryun. In 1964, he became the first high-schooler to break the 4-minute mile, and in 1966 he set world records in the mile and half-mile runs. He won a silver medal in the 1500-meter run at the 1968 Olympic games. A Republican from Kansas, he served in the US House of Representatives 1997–2007.