Heavyweight unification series Heavyweight unification series The heavyweight unification series, also known as the Heavyweight World Series, was a sequence of professional boxing matches held in 1986 and 1987 to crown an undisputed champion of the heavyweight class. The series was produced by HBO Sports and promoted by Don King. It ended with Mike Tyson as undisputed champion, holding the championship belts of the International Boxing Federation, World Boxing Association, and World Boxing Council. Prior to the series, the last undisputed heavyweight champion had been Leon Spinks, who won the championship in his 1978 victory over Muhammad Ali. Spinks had been stripped of
Heavyweight boxing championship records and statistics single "Heavyweight Champion", is now referred to as the "Undisputed Champion" as the one fighter that has defeated all the other titlists. However, there is no officially declared definition of the term, as major boxing organizations refer to all boxers holding at least two world titles in their respective division as "Unified champions". Some title reigns are not recognized as official reigns due to long periods of inactivity, legitimacy of title, false billing and promotion. In March 1967, Muhammad Ali was systematically denied a boxing license in every state and stripped of his passport because of his refusal to be