Ukraine's former world heavyweight champion Wladimir Klitschko announced his retirement from boxing on Thursday to scupper any hopes of a November rematch against Britain's Anthony Joshua.

Hamburg-based Klitschko, 41, hangs up his gloves as one of the all-time greats of the ring after a nine-and-a-half year reign as heavyweight champion, which was ended in 2015 and his last two fights ended in defeat.

He is behind only the great Joe Louis as the second-longest serving heavyweight champion of all time having enjoyed 18 consecutive defences over a nine-year span. Louis made 26 title defences between 1937 and 1949.

Klitschko, nicknamed 'Dr Steelhammer' due to the PhD he holds, won super-heavyweight gold at the 1996 Atlanta Olympic Games.

Wladimir Klitschko reigned as heavyweight champion for nearly a decade

After turning professional, he was the undisputed world champion from 2006-2015, a period in which he held several belts.

His reign was ended two years ago when he finally lost to Britain's Tyson Fury on points.

Klitschko's last fight was in April when he was stopped by Joshua in the 11th round of the WBA title fight in front of 90,000 at Wembley Stadium in London in a hard-fought bout in which both fighters hit the canvas.

Klitschko's retirement dashes a mooted blockbuster rematch with Joshua possibly in Las Vegas in November.

- 'End of an era' -

Such was the interest in Klitschko's announcement that the demand crashed his website on Thursday morning.

"After my last fight against Anthony Joshua, I deliberately took the time to make a decision," said Klitschko, whose elder brother Vitali, 46, is also a former world heavyweight boxing champion.

"I never thought I'd have such a long and incredibly successful boxing career, I thank you all from the bottom of my heart," he told his fans in a statement.

Klitschko bows out with a record of 64 wins and five defeats with 54 knock-out wins in 69 professional bouts.

"This retirement marks the end of an era that is unrivaled in the sporting world," said Frank Hoffmann, the head of RTL who broadcast Klitschko's fights in Germany.

Wladimir never boxed his brother Vitali to honour a promise both boxers made to their mother, but the elder Klitschko brother hailed his sibling's glittering career.

"It was a great journey. For decades Wladimir was at the top of the world of boxing," wrote Vitali on his Facebook page.

"He won the Olympic gold, became the world champion many times and united all the professional belts.

"I can only wish someone will repeat the results he achieved".

Wladimir Klitschko said he was excited about the next stage of his career.

"I have achieved everything I dreamt of, and now I want to start my second career after sports," added Klitschko in a video statement.

"27 years ago, I started my journey and it was the best decision I could have ever made.

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

"I became a scientist, an entrepeneur, a hotelier, a motivator, a leader, a trainer, an investor and much more.

"I'm still able to do all this because of the global appeal of the sport of boxing.

- Hotel interests -

"At some point in our lives, we need or just want to switch our careers and get ready for the next challenges, I'm no exception.

"Now it is my turn, I'm honestly doing this with respect for the new challenges and also with tremendous excitement, passion and dedication.

"I am expecting and hoping that my next career, which I have been planning and working on for a few years, will be at least as successful as my old one."

Among his future projects, Klitschko will now turn his attention to the hotel industry.

He is involved in a chain of luxury hotels -- 11 Mirrors -- in Ukraine and has plans to expand.

"We are concentrating on expanding with 11 Mirrors to Germany and the USA," Klitschko told German finance magazine Euro am Sonntag.

"I like to spend a lot of money on the training of my employees.

"There is no better return on investment than investing money in its team."