The World Boxing Organization (WBO) is an organization which sanctions professional boxing bouts. It is recognized by the International Boxing Hall of Fame (IBHOF) as one of the four major world championship groups, alongside the World Boxing Association (WBA), World Boxing Council (WBC), and International Boxing Federation (IBF). The WBO's headquarters are located in San Juan, Puerto Rico.
Christopher Livingstone Eubank is a British former professional boxer who competed from 1985 to 1998. He held the WBO middleweight and super-middleweight titles between 1990 and 1995, and is ranked by BoxRec as the third best British super-middleweight boxer of all time.
Jackie Kallen is one of boxing's first and most successful female managers. Her life was the inspiration for the 2004 film Against the Ropes, starring Meg Ryan as Kallen, in which she had a brief speaking role as a reporter. She also worked as a consultant for Mark Burnett's reality TV series The Contender.
Anthony "The Bullet" Bonsante is a professional boxer and competitor on reality TV show The Contender. He also works overnight as a supervisor at a distribution center.
Jimmy Lange is a professional boxer from Virginia.
Juan Pedro de la Rosa is a Mexican professional boxer, and is the brother of welterweight boxer James de la Rosa.
Peter Manfredo Jr. is a former American professional boxer and former IBO middleweight champion. He has challenged twice for upper-level world titles, at middleweight and super middleweight, as well as having won the NABO, IBU and European Boxing Association (EBA) light middleweight titles.
Stephen Collins is an Irish former professional boxer who competed from 1986 to 1997. Known as the Celtic Warrior, Collins is the most successful Irish boxer in recent professional boxing history, having held the WBO middleweight and super-middleweight titles simultaneously and never losing a fight as champion.
In professional boxing, the undisputed champion of a weight class is the boxer who holds world titles from all of the major sanctioning organisations simultaneously. There are currently four major sanctioning bodies: WBA, WBC, IBF and WBO. There were many undisputed champions before the number of sanctioning bodies increased to four in 2007, but there have only been 10 boxers to hold all four titles simultaneously. As of November 2021, Josh Taylor and Canelo Álvarez are undisputed champions in the light welterweight and super middleweight divisions respectively.
Jeffrey Scott Lacy is an American former professional boxer who competed from 2001 to 2015. He held the IBF super middleweight title from 2004 to 2006, and the IBO super middleweight title from 2005 to 2006. Lacy rose to prominence in the early to mid-2000s as a feared puncher in the division, with his physique and knockout record making him one of boxing's top-rated prospects at the time.
Richie Woodhall is a British former professional boxer who competed from 1990 to 2000. He held the WBC super-middleweight title from 1998 to 1999, as well as the Commonwealth middleweight title from 1992 to 1995, and the European middleweight title from 1995 to 1996. As an amateur, Woodhall won a gold medal at the 1990 Commonwealth Games and bronze at the 1988 Summer Olympics, both in the light-middleweight division.
Avetik Abrahamyan, best known as Arthur Abraham, is an Armenian-German former professional boxer who competed from 2003 to 2018. He held multiple world championships in two weight classes, including the IBF middleweight title from 2005 to 2009, and the WBO super-middleweight title twice between 2012 and 2016.
Sakio Bika is a Cameroonian-Australian professional boxer. He held the WBC super-middleweight title from 2013 to 2014, and previously the IBO super-middleweight title from 2008 to 2010. In 2015 he challenged once for the unified light-heavyweight world title, and in 2007 won the third season of The Contender reality TV series.
Kelly Robert Pavlik is an American former professional boxer who competed from 2000 to 2012. He won the unified WBC, WBO, Ring magazine and lineal middleweight titles by defeating Jermain Taylor in 2007, and made three successful defenses before losing them to Sergio Martínez in 2010.
Joseph William Calzaghe is a Welsh former professional boxer who competed from 1993 to 2008. He held world championships in two weight classes, including the unified WBA (Super), WBC, IBF, WBO, Ring magazine and lineal super-middleweight titles, and the Ring light-heavyweight title.
Joe Calzaghe versus Mikkel Kessler was a super middleweight boxing contest between the number one and two super middleweights in the World. At the time both fighters were unbeaten. On the line was the WBO, WBC and WBA World belts as well as The Ring Magazine championship. Calzaghe won by unanimous decision.
Bernard Humphrey Hopkins Jr. is an American former professional boxer who competed from 1988 to 2016. He is one of the most successful boxers of the past three decades, having held multiple world championships in two weight classes, including the undisputed middleweight title from 2001 to 2005, and the lineal light heavyweight title from 2011 to 2012.
Daniel MacKinnon is a retired New Zealand professional Light Heavyweight, Super Middleweight and Middleweight boxer. MacKinnon has entered the WBO top 15 rankings multiple times, peaking at #12 in the Super Middleweight Division in November 2008 and #12 in the Light Heavyweight Division August 2013.
Mger Mkrtchyan (born 12 November 1976 in Gyumri, Armenia is an Armenian former professional boxer, who held the EBU Super Middleweight and the WBO Asia Pacific super middleweight title, as well as being a contender for the WBO World Super middleweight title, losing against Joe Calzaghe in the 7th-round due to a technical knockout.
Branko Sobot is a Croatian former professional boxer, who held the IBF Inter-Continental middleweight and super middleweight titles and challenged for the WBO World Super middleweight title, losing against Joe Calzaghe by 3rd round TKO.
Jimmy Lange 
Juan de la Rosa 
Kit Munroe
Errol Brown