Mike Tyson hold the record for the youngest heavyweight champion of the world at 20 years, 4 months and 22 days old
It is Mike Tyson when he was fighting with Trevor Berbick He became the youngest heavyweight champion in history.
ali
Mohamed Ali
Muhammad ali
Rocky Marciano
Not at this time.
Rocky Marciano is the only heavyweight champion not to loose a fight.
joe louis
Joe Louis
Of boxing...honestly, who cares anymore.
geroge forman