Fernando Broke the record of Emerson Fittipaldi a Brazilian who won the world championship when he was only 25 years old. He accomplished this feat in 1972 as he won 5 out of the 11 races that season and easily won the world title from Jackie Stewart. His record was broken by Alonso who became a world champion at the age of 24 years and 58 days.
Lewis Hamilton (UK) won the 2008 Formula 1 world championship at age 23, the youngest in history.
At the moment it is Sebastian Vettel who won the Championship in 2010 and was 22