Former world champion Wladimir Klitschko announced his retirement from boxing on Thursday.
Klitschko, 41, was considering a rematch with Anthony Joshua, who scored an 11th round knockout of Klitschko in April.
"I deliberately took a few weeks to make my decision, to make sure I had enough distance from the fight at Wembley Stadium. 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," Klitschko said in a statement.
"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."
Klitschko finishes his career with a record of 64–5 with 53 knockouts and endured one of the longest unbeaten title defense runs in the sport's history.
He had 23 successful title defenses in a two-decade career and lost his WBA IBF, WBO titles in 2015 after a unanimous decision defeat to Tyson Fury.
He started his career after winning the Olympic gold at the 1996 Summer Olympics in Atlanta.