The answer is former WBA Heavyweight Champion of the World, Nikolai Valuev.
Probably Pacquiao WBO Welterweight champion Ring Magazine / IBO Jr Welter champion WBC Lightweight champion WBC / Ring Magazine Jr lightweight champion Ring Magazine Featherweight champion IBF Jr Featherweight Champion WBC Flyweight Champion Actually Oscar Delahoya is the only true 6 weight class champion. He won MAJOR titles in all 6. If it is most boxing championships (major and minor, regardless of division) that would be Roy Jones Jr. IBF - Middleweight Champion IBF- Super Middleweight Champion WBC- Lightheavyweight Champion (3 times) WBA Light Heavyweight Champion WBA Super Light Heavyweight Champion WBA - Heavyweight Champion IBF Light Heavyweight Champion IBO Light Heavyweight Champion Ring Magazine - Light Heavyweight Champion IBA - Light Heavyweight Champion WBF - Light Heavyweight Champion NBA - Light Heavyweight Champion IBC - Light Heavyweight Champion NABO - Light Heavyweight Champion (2 times) WBC Continental Americas - Super Middleweight Champion UBO - Intercontinental Light Heavyweight Champion
Vladimir Klitschko is the IBF, WBO, WBA and IBO champion Vitali Klitschko is the WBC champion
= Wladimir Klitschko is the IBF, WBO & IBO Heavyweight Champion. = = Ruslan Chagaev is the WBA Heavyweight Champion = = Oleg Maskaev is the WBC Heavyweight Champion =
Michael Moorer. WBA, WBO, IBF Heavyweight champion of the world(1992-1994). Former WBO light Heavyweight champ(1988-1990).
The current Heavyweight champions are: WBA Nikolay Valuev Russia WBC Vitali Klitschko Ukraine IBF,WBO & IBO Wladimar Klitschko Ukraine
First Hispanic World Heavyweight ChampJohn Ruiz, former two-time WBA World Heavyweight champion, although he was born in Methuen, Massachusetts.
1993 and 1995 United States amateur Light Heavyweight champion.1994 National Golden Gloves Light Heavyweight championWon the Light Heavyweight bronze medal for the United States at the 1996 Olympics in AtlantaWon WBU, WBC. IBF, WBA. IBO WBF, IBA & NBA Light Heavyweight titles
well, the current white heavyweight champions are Sultan Ahmed Ibragimov WBO Ruslan Chagaev WBA Oleg Maskaev WBC Wladimir Klitschko IBF The last non white champion and incidently the last americn champion was Shannon "Brooklyn" Briggs who lost in 2007
Klitschko defeated Haye via a unanimous decision to capture the WBA belt and become the unified WBA, WBO, IBF and IBO Heavyweight Champion.