The 41-year-old Ukrainian icon united the heavyweight division and held the World Boxing Association (WBA), International Boxing Federation (IBF), World Boxing Organization (WBO) and International Boxing Organization (IBO) world titles during an illustrious career.

He also won the super-heavyweight gold medal at the 1996 Olympic Games in Atlanta.

His retirement comes after two consecutive defeats against British boxers - Tyson Fury and Anthony Joshua.

"I have achieved everything I dreamed of, and now I want to start my second career after sports," said Klitschko, who was renowned for his formidable punching and will go down as all-time great.

"I would have never imagined that I would have such a long and incredibly successful boxing career.

"Twenty-seven years ago I started my journey in sport. 

"It was the best choice of a profession I could have made. 

"Because of this choice I have travelled the world, learned new languages, created business, built intellectual properties, helped people in need.

"At some point in our lives we need to switch our careers and get ourselves ready for the next chapter - obviously I am not an exception to this.

"I am expecting and hoping my next career, which I have already been planning and working on for some years, will be at least as successful as the previous one, if not more successful."

Klitschko won his first professional fight against Mexico's Fabian Meza in Hamburg in November 1996 after his decision to leave the amateur ranks following the Atlanta Games.

Undefeated in his first 24 bouts, he lost for the first time in his only fight in Ukraine as American Ross Puritty claiming a technical knock-out win in Kyiv in 1998.

He won his first heavyweight world title by clinching the WBO crown against American Chris Byrd in 2000, but lost it in 2003 after a surprise defeat to South African Corrie Sanders.

A year later, he failed in a bid to regain the belt after losing to American Lamon Brewster on April 10, 2004.

That was to be his last defeat until 2015 when he lost to Fury.

He beat Byrd again to win the IBF and IBO titles in 2006 and added the WBO and WBA (Super) titles with wins over Russia's Sultan Ibragimov and Britain's David Haye in 2008 and 2011 respectively.

After a string of defences, Klitschko, who largely based himself in Germany, lost all of the belts to Fury in Düsseldorf.

He then lost his final fight to London 2012 Olympic champion Joshua on April 29 this year, failing in a bid to win back the IBF title at Wembley Stadium after a titanic contest.

Wladimir is the younger brother of Vitali Klitschko, himself a former world heavyweight champion and now the Mayor of Kyiv. 

His career finishes with 64 victories - 53 via knock-out - and five defeats. 

A rematch with Joshua had been tipped before his retirement.