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 of 23, 2019. These lists do not include "The Ring" and lineal championship fights after 1921, although they only include title streaks during which the champion captured "The Ring" or lineal title. Keys: As of 23, 2019. As of 23, 2019. Keys: "As of 24 September 2018". This list includes only major titles, and it does not include lineal championships after 1921. Below is a list of longest reigning heavyweight champions in boxing measured by the individual's longest reign. The list includes both "The Ring" and lineal championships. Career total time as champion (for multiple time champions) does not apply.