Cancer-hit badminton star Lee Chong Wei announced his retirement on Thursday, ending a brilliant career in which he collected a swathe of honours but never won a world or Olympic title.

Lee, who spent a total of 348 weeks as world number one but lost six world and Olympic finals, wept as he called it quits months after fighting off nose cancer.

“My decision to retire is a heavy one. I really love this sport. But it is a demanding sport. I thank all Malaysians for the past 19 years,” Lee, 36, told a news conference.

Lee, a father of two, was diagnosed with early-stage nose cancer last year and after intensive treatment in Taiwan, he said he was keen to play again. But he hasn't trained since April and after missing a series of self-imposed deadlines to return to competition, his hopes of being eligible for next year's Tokyo Olympics were remote.

The three-time Olympic silver medallist said he now wanted to rest and spend time with his family, and even take his wife on a “honeymoon”, a trip that has been delayed since their marriage in 2012.

He finishes his career with 705 wins and 69 titles, including five Commonwealth Games gold medals, four All England victories and a record 47 superseries triumphs.

Lee's unsuccessful attempts to capture Malaysia's first ever Olympic gold medal, reaching three consecutive finals, were followed avidly by his fans, as was his long-running rivalry with Chinese superstar Lin Dan.

His last shot at the Olympic title at Rio 2016 ended in crushing disappointment when the Malaysian lost out to China's Chen Long in a nail-biting final.

Lin posted to his four million followers on China's Twitter-like Weibo: “I will be alone on the [badminton] court and no one will accompany me.” He also posted a link to a Chinese ballad called “Friends Don't Cry”.

“Lin Dan and myself are rivals in the court but outside the court, we are close friends,” Lee said when asked about their rivalry.

“I hope Lin Dan will play in the Tokyo Olympics. But he faces challenges from younger players.”

'Lee is a legend'

Cancer proved the career-ending blow but it wasn't the only low for Lee, who was banned after testing positive for a banned anti-inflammatory at the 2014 world championships.

The long-time former world number one returned to the sport in 2015, after authorities accepted he took the drug inadvertently.

“I have no regrets. More important is my health, the decision to retire is very tough,” said Lee, adding that his cancer treatment was now over.

“My plan to retire was originally after the Olympic Games. I made this decision due to my health."

“You know I got married in 2012. But we (have) never gone for a honeymoon. I owe this promise [to my wife], now I have to please her,” he said.

Lee said that at his last check-up in Taiwan in April he was told by his doctor to rest as “badminton requires high-intensity training”.

Badminton Association of Malaysia (BAM) President Norza Zakaria, who was at the news conference, described Lee as a “legend”.

“It is a sad day. Lee is a legend and very dependable. We accept his decision,” Norza said.

Malaysian Sports Minister Syed Saddiq Syed Abdul Rahman described Lee as “a hero to all Malaysians... someone like him comes once in a lifetime”.

He said Lee will be the chief of mission for the Malaysian contingent to the Tokyo Games. As he began announcing his retirement, Lee paused for almost a minute as tears rolled down his cheeks.

"I fought for my country all the way," said Lee, now down at 191 in the rankings.

"It's my retirement day."