Wladimir Klitschko (born 25 March 1976) is a Ukrainian former professional boxer who competed from 1996 to 2017, holding multiple heavyweight world championships between 2000 and 2015, including unified titles and the IBO and Ring magazine belts. Known for his exceptional knockout power and athletic footwork, he sharpened his tactical thinking by playing blitz chess with Garry Kasparov, and as an amateur he won a gold medal at the 1996 Olympics. After early upset losses to Corrie Sanders (2003) and Lamon Brewster (2004), he hired trainer Emanuel Steward, transitioning to a more defensive style and, alongside his brother Vitali, dominating the division during the "Klitschko Era" from 2004 to 2015. He set all-time records for the longest time as world heavyweight champion (4,382 days) and most fighters beaten for the title (23), with his fights reportedly drawing up to 500 million viewers. Born in Kazakhstan to a Soviet Air Force major general, he and his brother Vitali (now Mayor of Kyiv) lived in Pripyat during the Chernobyl disaster, and he was inducted into the International Boxing Hall of Fame in 2021.