Nadia Comaneci, Romanian Gymnast: At just 14, Nadia Comaneci was an Olympic princess at the 1976 Montreal Games. She was the first gymnast to ever receive a perfect 10 for her routine on the uneven bars. She didn't stop there, earning six more perfect scores and becoming the youngest all-around gymnastics gold medalist. The Romanian won a total of nine medals over the course of her Olympic career, five of them gold.
Marjorie Gestring, American Diver: Marjorie Gestring took the 1936 Berlin Olympics by storm when she was just 13 years old and won a gold medal in the 3m springboard contest. The 1936 games were her only Olympic appearance, but Gestring went down in history as one of the youngest Olympians ever to win a gold medal.
Tom Daley, British Diver: Tom Daley made his Olympic debut in Beijing in 2008 at age 14. The British diver didn't take home any medals from the Beijing Games, but made quite a splash for being the youngest member of the British Olympic team that year. He'll compete again in London this summer.