Former world heavyweight champion Wladimir Klitschko announced his retirement from boxing on Thursday after a 21-year career that culminated in a loss to Anthony Joshua in April. Boxer Wladimir Klitscko Retirement The 41-year-old Ukrainian Klitschko made the announcement on his YouTube channel early Thursday morning, and also shared the video on Twitter: Wow! So many people interested in my statement. Server broke down. So look here…https://t.co/iZnjFtxHeT — Klitschko (@Klitschko) August 3, 2017 The announcement came amid rumors of a rematch between him and England's 27-year-old Joshua. That bout — held before a sold-out crowd of 90,000 at London's Wembley Stadium on April 29 — marked Klitschko's 29th heavyweight title fight appearance. Klitschko went down three times overall in the bout and was stopped in the 11th round, thus failing to defend his title. That was Klitschko's second straight defeat after a huge upset loss to Tyson Fury 17 months prior that cost him the unified world championship he had held for nearly ten years. Klitschko (64-5, 54 KOs) had the right to an immediate rematch against Joshua, whose promoter Eddie Hearn of Matchroom Boxing had begun coordinating with the Ukrainian's team to set up another fight. Both camps had set a Nov. 11 date for a rematch in Las Vegas, but Klitschko backed out at the last minute. I heard the news this morning from Bernd Boente that Wladimir Klitschko has decided to retire from boxing. We wish him all the success ?? — Eddie Hearn (@EddieHearn) August 3, 2017 "I deliberately took a few weeks to make my decision, to make sure I had enough distance from the fight at Wembley Stadium," Klitschko said. "As an amateur and a professional boxer, I have achieved everything I dreamed of, and now I want to start my second career after sports. I would have never imagined that I would have such a long and incredibly successful boxing career. I'm very thankful for this. Thanks to everyone who has always supported me especially my family, my team and my many fans." Hearn admitted he was disappointed there will not be a rematch but paid tribute to Klitschko, per MailOnline's Riath Al-Samarrai: "We are obviously disappointed from an event perspective because the rematch was huge, but from a personal perspective I am happy for Wladimir," said Hearn, who learned of Klitschko's retirement from the Ukrainian's manager, Bernd Boente on Thursday. "He has had a tremendous career and leaves with a great legacy, in great health and with everything he needs in life. He could have made millions for this fight, but he already has millions." WATCH: Wladimir @Klitschko announces retirement from boxing. More here: https://t.co/Gok3TH0hqe #SSN https://t.co/t5fvbvweuY — Sky Sports News (@SkySportsNews) August 3, 2017 Klitschko first rose to fame in Germany, where he fought in sold-out soccer stadiums across the nation. However, he also spends much time in the United Sates, where he and his longtime fiancée — actress Hayden Panettiere — are raising a toddler daughter. The 6-foo-6, 240-pound Ukrainian is one of the most decorated boxers in history: he won the Olympic super heavyweight gold medal as an amateur in 1996, and was a two-time world champion as a professional. "Especially after this terrific fight at Wembley Stadium it was a very tough decision for Wladimir to make," Boente said. "But he has always emphasized that he wanted to retire if he didn't have enough motivation anymore. Therefore this is definitively the right decision. Wladimir accomplished everything in his unique boxing career. He dominated the heavyweight division for over a decade. He fought in sold-out arenas and stadiums worldwide and millions of fans around the world watched his fights on TV. It has been a privilege for me to accompany Wladimir on this unique journey." Klitschko's second reign as world heavyweight champion lasted 9 years, 7 months and 7 days (from April 2006 to Nov. 2015), the second-longest heavyweight title tenure in history behind only legend Joe Louis, who held the title for 11 years, 8 months and 8 days. Klitschko's reign ended with his loss to Fury. During the reign, Klitschko made 18 consecutive defenses, third-most in division history behind only two other legends, Louis (25, the all-time record for any weight class) and Larry Holmes (20). "Twenty-seven years ago [as an amateur] I started my journey in sports and it was the best choice of a professional I could have ever made," Klitschko said. "Because of this choice, I've travelled the world, learned new languages, created businesses, built intellectual properties, helped people in need, became a scientist, entrepreneur, motivator, hotelier, trainer, investor and much else. I was and am still capable of doing all this because of the global appeal of the sport of boxing. "At some point in our lives we need to, or just want to, switch our careers and get ourselves ready for the next chapter and chart are new course toward fresh challenges. Obviously, I'm not an exception to this and now is my turn. I'm honestly doing this with the greatest respect for the new challenges, but also with tremendous excitement, passion, dedication expecting and hoping that my next career, which I've already been planning and working on for some years, will be at least as successful as my previous one. "Finally, instead of just saying thanks and goodbye, I want you to continue to enjoy me in this new and exciting journey. When we're together we're more creative, more efficient, more productive and simply stronger in every way. Together we're the driving force." LONDON, ENGLAND - APRIL 29: Anthony Joshua (White Shorts) and Wladimir Klitschko (Gray Shorts) in action during the IBF, WBA and IBO Heavyweight World Title bout at Wembley Stadium on April 29, 2017 in London, England. (Photo by Richard Heathcote/Getty Images)