Juan Manuel Fangio, Argentina

He is one of the pioneers of Formula 1 and dominated the field in the 1950s. After winning his first championship in 1951, he ventured into other forms of racing over the next couple of years. But upon his return to F1, Fangio resumed where he left off and won four straight championships from 1954 to 1957. 

The great thing about Fangio was that he won 5 champioships with 5 different teams. He also won 24 out of the 51 starts he made in F1!

-Picture courtesy Wiki Media-