[11][12] In 2006, Wladimir regained a portion of the world heavyweight championship after defeating Byrd in a rematch to win the International Boxing Federation (IBF) and IBO titles.

After defeating Alexander Povetkin in October 2013 and until his loss to Tyson Fury in November 2015, Klitschko was recognised as the lineal champion by the Transnational Boxing Rankings Board (TBRB).

Klitschko turned professional with Universum Box-Promotion in Hamburg under the tutelage of Fritz Sdunek, often being featured on fight cards alongside his elder brother Vitali.

At the start of the eleventh round, with Puritty continuing to land hard punches, Klitschko's trainer, Fritz Sdunek, entered the ring and stopped the fight.

[64] In a fight that was aired on pay-per-view in the United Kingdom,[65] Wladimir won the WBO world heavyweight title from Byrd by a wide unanimous decision (UD) with scores of 120–106, 119–107, and 118–108, flooring his opponent twice.

The fight took place at Hanns-Martin-Schleyer-Halle in Stuttgart, the same venue where Botha had fought Axel Schulz for the IBF title six years earlier, in the most watched boxing match in German TV history.

[80][81] Klitschko had his next title defence scheduled three months later, on 29 June 2002 at Etess Arena in Atlantic City, New Jersey, against former WBO heavyweight champion Ray Mercer.

McCline, having made his professional boxing debut in 1995, became an established contender after defeating Michael Grant, knocking him down with the first punch thrown and ultimately stopping him in 43 seconds.

[91] After failing to reach agreements with Kirk Johnson, Fres Oquendo, Lou Savarese and Danny Williams, Universum ultimately signed a 4-fight contract with Corrie Sanders, who was ranked No.9 contender by WBO at the time.

[93] After winning two minor bouts in Germany and enlisting the services of legendary boxing trainer Emanuel Steward, Klitschko again fought for the vacant WBO title on 10 April 2004, in Las Vegas, against Lamon Brewster.

[94] Judd Bernstein, the lawyer representing Klitschko, suggested that he was a victim of an ongoing fight fixing in Las Vegas (which also included fraudulent medical reports), which was investigated by FBI at the time.

[132] In the opening rounds, Brock's economical but effective movement made Klitschko reluctant to throw punches, with Wladimir not being able to fully establish his rhythm.

[137] By the end of October 2007, Wladimir Klitschko started negotiations with then-WBO world heavyweight champion Sultan Ibragimov about the unification showdown in the near future.

[162] Boxing journalist Phil Santos pointed out that Klitschko fought for the majority of the fight "only with his left hand", proving once again that he "is the best heavyweight in the world right now".

The fight took place at Color Line Arena in Hamburg, Germany, the same venue where Thompson had defeated then-highly regarded German boxer Luan Krasniqi in a WBO world heavyweight title eliminator almost a year prior.

[173] In the post-fight interview, Klitschko admitted that the fight turned out to be tougher than expected: "It is not so easy to defend all the titles and it has been a while since I last had a black eye so today I really look like a boxer.

Ultimately, Klitschko reached agreements with Chagaev who agreed to step in for Haye as a last-minute replacement (Valuev's team wanted the fight to be postponed until autumn of that year).

[190][191] In the pre-fight comparison, The Ring was giving Klitschko an advantage in power, speed and athletic ability, as well as experience, while also crediting Chagaev for having better defence, praising him for his fundamentals and footwork.

This mandatory title defence, originally scheduled for December 2009, had to be delayed due to a hand injury that Klitschko sustained in training that required surgery.

[197] In the pre-fight comparison of the fighters, The Ring gave Chambers the upper hand in speed and athletic ability, as well as defence, while crediting Klitschko as more powerful and experienced.

[197][201] The bout turned-out to be one-sided, with the champion winning rounds keeping Chambers at the end of his jab and occasionally throwing straight right hands.

[233] Haye revealed afterwards that he had a broken toe on his right foot, and claimed that it had hindered his game plan for the fight as he felt he was unable to jump out at Klitschko like he had previously in his career.

[250] "I've been waiting for this rematch for so long", Thompson said during one of pre-fight press-conferences, "In Bern, I'm gonna finish what I've started 4 years ago - knock Klitschko out and take the belts back to the United States".

On 23 September, Fury again postponed the fight after being declared "medically unfit",[354] before eventually vacating the WBA (Super), WBO, and IBO titles, citing problems with depression after testing positive for cocaine.

Days after the Fury rematch was called off, Klitschko was approached by Eddie Hearn, promoter of IBF champion Anthony Joshua, to fight on 28 November date they had set for a second defence.

[362] WBA president Gilberto Jesus Mendoza confirmed that the winner will have to face mandatory challenger Luis Ortiz next, with deadlines due to be set after the unification fight.

[378] On 11 July 2017, Eddie Hearn travelled to the US to apply for a Nevada boxing licence for promoting and to also scout potential locations in Las Vegas speaking to MGM.

[379] Hearn told Sky Sports, "We met with Richard Sturm and the team at MGM in Las Vegas yesterday and had a full tour of the T-Mobile Arena which is very impressive.

[398][399][400] Considered national heroes in Ukraine, in 2008 the Klitschko brothers were ranked number 15 in Inter's list of the 100 Greatest Ukrainians following a nation-wide poll that saw around 2.5 million people casting their votes.

[483] In November 2024, Klitschko issued a request to American podcast host Joe Rogan to have him on his show in order to discuss their differences regarding the Ukraine-Russia conflict.