Ali, Louis and Tyson: Who is the greatest heavyweight of all-time?
John L. Sullivan won boxing's first heavyweight title in 1885 and made the first defence of his belt seven years later against James J. Corbett, who then became the only man to defeat the legendary Sullivan.
Elsewhere, Muhammad Ali is the only heavyweight to have won the lineal title on three occasions while Tyson Fury, Lennox Lewis, Floyd Patterson, Evander Holyfield and George Foreman have won the championship twice.
"Big George" is the oldest heavyweight world champion at the age of 45 while 'Iron' Mike Tyson is the youngest at 20.
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5) Rocky Marciano
His 49-0 record was finally beaten in 2017 when Floyd Mayweather defeated Conor McGregor to go 50-0.
4) Jack Dempsey
Dempsey's popularity attracted the first million-dollar gate. In 1919, Dempsey won the lineal strap with a destructive victory over Jess Willard. It was a three-round demolition which saw Willard knocked down SEVEN times in the opening round.
3) Jack Johnson
Dealing with racism and discrimination his whole life, Johnson is celebrated among society as the man who paved the way for a new generation of fighters in the sport. Johnson's record is 72-11-11 (3).
More than 100 years after being convicted for violating the Mann Act, president Donald Trump granted full pardon to Johnson in 2018.
2) Joe Louis
Louis retired as the champion in 1949 before making two comebacks. Louis would again hang the gloves up in 1951 with a 66-3 record after losing to Marciano.