Former heavyweight world champion Wladimir Klitschko has retired from boxing – ruling out a rematch with Britain's Anthony Joshua.
The Ukrainian, 41, was knocked out in the 11th round by current champion Joshua at Wembley Stadium in April.
Joshua, 27, had hoped Klitschko would sign his rematch clause for a proposed fight in Las Vegas on 11 November.
"I have achieved everything I dreamed of, and now I want to start my second career after sports," said Klitschko.
The two-time former champion, who held the unified title from 2006-2015 before losing to Joshua's fellow Briton Tyson Fury, ends his career with a record of 64 wins and five defeats.
"I would have never imagined that I would have such a long and incredibly successful boxing career," he added.
Joshua must now face mandatory challenger Kubrat Pulev before 2 December or risk being stripped of his IBF belt. Bulgarian Pulev, 36, has a record of 25 wins and one defeat, which came to Klitschko in 2014.
Klitschko won Olympic super-heavyweight gold at the 1996 Games in Atlanta, before turning professional later that year.
He built an unbeaten 24-0 record before losing to American Ross Puritty in 1998 in his only fight to take place in his native Ukraine.
After claiming the WBO belt with victory over American Chris Byrd in 2000, Klitschko was upset by South Africa's Corrie Sanders and American Lamon Brewster in 2003 and 2004 respectively.
He then went 11 years unbeaten, until losing the WBA, IBF and WBO titles to Fury in November 2015.
The Germany-based fighter announced his retirement on a video posted on his website, with so many people trying to access it that the server crashed.