Honorable Mention: Randy Couture, Tim Sylvia, Brock Lesnar
There have been multiple heavyweights to pick up two title defenses in the UFC. However, Fedor Emelianenko is the only heavyweight champion of a major MMA organization to defend his title three times. "The Last Emperor" also picked up a number of additional victories during his reign as Pride champion, giving him the edge over UFC heavyweights Randy Couture, Tim Sylvia and Brock Lesnar.
Some may argue that Couture deserves the nod over Emelianenko on this list, but the very fact that Couture was a three-time heavyweight champion is an example of Couture's lack of dominance in comparison with Emelianenko, as he was dethroned from the top of the UFC's heavyweight division three times. To be fair, though, one of those instances was due to a contract dispute.
In March 2003, Emelianenko defeated Antonio Rodrigo Nogueira to become the second Pride heavyweight champion. Well over one year later, after non-title fight wins over Gary Goodridge, Mark Coleman, Kevin Randleman and more, Emelianenko finally defended his belt for the first time against Nogueira, who had earned an interim title with a win over Mirko "Cro Cop" Filipovic.
After beating Nogueira for a second time, Emelianenko picked up two more title defenses against Filipovic and Mark Hunt before the Pride organization was purchsed by Zuffa and discontinued. Between those victories, Emelianenko scored another submission win over Mark Coleman in a non-title bout
Following the downfall of Pride, Emelianenko defeated Sylvia to win the WAMMA heavyweight title, which never really gained notoriety due to the exploding popularity of the UFC. However, the Russian heavyweight defended that title against Andrei Arlovski and Brett Rogers before going on a three-fight skid that has essentially derailed his career.