China's two-time Grand Slam winner Li Na has announced her retirement after failing to overcome "chronic" injuries.
The 32-year-old world number six won the Australian Open in January to add to her 2011 French Open title.
However, she had not played since losing in the third round at Wimbledon in June and underwent knee surgery in July.
"Walking away from the sport, effective immediately, is the right decision for me and my family," she said.
"It took me several agonising months to finally come to the decision that my chronic injuries will never again let me be the tennis player that I can be."
|A Chinese trailblazer|
|Li was hand-picked to train in China's Soviet-style sports system aged nine.|
|She was initially identified as a badminton player before being moved into tennis.|
|After giving up the game to study at university, she returned to the tour in 2004 and won her first WTA title in Guangzhou.|
|Li became the first Chinese to reach a Grand Slam quarter-final, at Wimbledon in 2006.|
|She entered the world's top 10 in 2010 after reaching the 2009 US Open quarter-final and 2010 Australian Open semi-final.|
|Reached her first Grand Slam singles final at the 2011 Australian Open, losing to Kim Clijsters.|
|Beat Francesca Schiavone to win the 2011 French Open at the age of 29.|
|Won her second Grand Slam title by beating Dominika Cibulkova at the 2014 Australian Open.|
Li rose to be a national sporting hero in China after becoming Asia's first Grand Slam singles champion and only America-based Russian Maria Sharapova has higher off-court earnings, according to the Forbes list of highest paid female athletes.
Announcing her decision in an open letter to fans, she added: "After four knee surgeries and hundreds of shots injected into my knee weekly to alleviate swelling and pain, my body is begging me to stop the pounding.
"While I've come back from surgery in the past, this time it felt different. As hard as I tried to get back to being 100%, my body kept telling me that, at 32, I will not be able to compete at the top level ever again."
Li has been instrumental in the growth of tennis in China and said she would always be proud of her achievements, adding she would now focus on plans to continue to grow the sport in her home country, including the creation of her own tennis academy.
Paying tribute to Li's achievements, Women's Tennis Association (WTA) chief executive Stacey Allaster said: "I am sad to hear that she has retired.
"In addition to her amazing tennis abilities and her warm and humorous personality, she is a pioneer who opened doors to tennis for hundreds of millions of people throughout China and Asia. Her legacy is immense and I have no doubt that her contributions to the WTA will be seen for decades to come.
"It's hard to be a household name in a nation with 1.4 billion people, but that's what Li Na is."
Swiss tennis legend Martina Hingis also credited the player's influence on the game in China, which now hosts six women's tour events.
She said: "It's a sad day for Chinese tennis and for the global sport in general."
|BBC tennis correspondent Russell Fuller|
|"An estimated 116 million people in China alone watched Li Na make history at Roland Garros in 2011. The following day she appeared, in a place normally reserved for politicians, on the front page of the People's Daily, and lucrative deals to endorse cars, running shoes and ice cream soon followed. Even though there is not yet any indication of the emergence of another Chinese player of her ability, Li Na's influence has been massive. Serena Williams and Maria Sharapova have just arrived in her home town of Wuhan to contest one of six events now staged on the WTA tour."|