Randy Orton was the youngest World Heavyweight Champion
Lewis Hamilton (UK) won the 2008 Formula 1 world championship at age 23, the youngest in history.
Brock Lesnar won the world heavyweight championship at the age of 24
Sebastian Vettel is the youngest ever formula one driver to win the driver world championship. Before him this record was held by Fernando Alonso and Lewis Hamilton. Vettel also holds other youngest records like the youngest driver to win 2, 3 and 4 titles back to back.
Mike Tyson was the youngest man to ever win a heavyweight boxing title but Floyd Patterson is the youngest ever undisputed world champion, though Patterson never fought in the multi commission ruled era of the WBC, WBA, & IBF.
When he was 15 Ian Thorpe won the 400 meter freestyle at the world championships. This made him the youngest male swimming world champion ever.
Randy Orton at the age of 24 was the youngest person to hold a title belt in the WWE. That title belt just happen to be the World Heavyweight Championship belt.
Stephen Hendry, at 21 years 106 days old in 1990.
Michael Phelps in swimming
Steven Hendry is the youngest ever. Previous to him it was Alex Higgins.
The youngest basketball player ever to win a championship in the finals was ................ Michael Jordan 23 from The Chicago Bulls
Sebastian Vettel is the youngest f1 race champion. He holds the following youngest records in formula one: a. He is the youngest ever double, triple and quadruple world champion in formula one history b. He has won 4 consecutive formula 1 drivers titles in his career c. He is the youngest ever driver to score championship points in formula 1 d. He is the youngest ever driver in formula 1 to secure pole position e. He is the youngest ever driver to win a formula 1 race