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 (IBF), World Boxing Association (WBA), and World Boxing Council (WBC).

Tim Witherspoon is an American former professional boxer who competed from 1979 to 2003. He was a two-time world heavyweight champion, having held the WBC title in 1984, and the WBA title in 1986. He beat Heavyweight World Champions Greg Page, James Smith, Tony Tubbs, Frank Bruno and Cruiserweight World Champions Alfonzo Ratliff and Al Cole. He is best known for his fight against undefeated Heavyweight World Champion Larry Holmes in which he lost by Split decision. Witherspoon also worked as a regular sparring partner for Muhammad Ali.