Iron Mike Tyson was the youngest heavy weight champion ever at 20 years old.
Wilfredo Benitez won a professional world title when he was 17 years of age
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.
Steven Hendry is the youngest ever. Previous to him it was Alex Higgins.
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.
The current F1 world champion is Sebastian Vettel from Germany. He is the youngest ever world champion.
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Wilfred Benitez is the youngest (male) world champion in boxing history, capturing the WBA junior welterweight title at the age of 17 years and 5 months with a split decision over Antonio Cervantes. He went on to win the WBC welterweight title as well as the WBC light middleweight title. = =
Randy Orton was the youngest World Heavyweight Champion
He was world heavyweight boxing champion from 1952 until his retirement in '56.