Rafael Nadal is retiring from professional tennis at 38, after winning 22 grand slam titles during an unprecedented era he shared with rivals Roger Federer and Novak Djokovic.

Nadal has competed infrequently the past two seasons because of injuries and said next month's Davis Cup finals will mark his farewell to the sport. He had hip surgery in 2023 and has entered just two of the past eight majors.

"The reality is that it has been some difficult years, these last two, especially. I don't think I have been able to play without limitations," Nadal said on Thursday.

"It is obviously a difficult decision, one that has taken me some time to make. But in this life, everything has a beginning and an end."

Nadal's unrelenting, physical style of play — every point pursued as though it were his last, sprinting and sliding into place for that high-bouncing bullwhip of a lefty forehand — made him one of the greats of the game and the unquestioned 'King of Clay', the slow, red surface on which he dominated.

His record 14 French Open championships are more than anyone, man or woman, won at any one of the sport's four major tournaments, a dominance celebrated by a statue of Nadal that stands near the main entrance to the grounds of Roland Garros.

In a result that symbolised where things stood for his body, and career, he exited in the French Open's first round this year, a straight-set loss to eventual runner-up Alexander Zverev.

Nadal returned there for the Paris Olympics, where he lost to old rival Djokovic in the second round of singles. He hasn't played since.

In addition to his French Open monopoly, Nadal won four trophies at the US Open and two apiece at Wimbledon and the Australian Open, giving him a career grand slam twice over.

"I think it is the appropriate time to put an end to a career that has been long and much more successful than I could have ever imagined," Nadal said.

His last pair of major titles arrived in 2022, at Melbourne in January and at Paris in June, pushing him ahead of Federer.

Both have since been surpassed by Djokovic, 37, who is up to 24 majors.

So much of Nadal's success was seen, fairly or not, through the prism of his encounters with Federer and Djokovic.

The tennis world, and plenty outside of it, were consumed with the debate over which was most deserving of the "GOAT" — "Greatest Of All-Time" — moniker. The world, tennis or otherwise, was fascinated by their matchups, their differing styles and personalities.

Who among those who witnessed it could possibly forget Nadal v Federer in the 2008 Wimbledon final? Or Nadal v Djokovic in the 2022 French Open quarters? Or Nadal v Djokovic in the 2012 Australian Open final? And so on.

Nadal played Djokovic 60 times, a record for two men in the Open era. Djokovic won 31-29 overall, while Nadal led 5-4 in slam finals. Nadal met Federer 40 times, Nadal winning 24-16, including 6-3 in slam finals.

"Thank you for the unforgettable memories and all your incredible achievements in the game we love," Federer told Nadal via social media.

Nadal's overall resume is unimpeachable: a total of 209 weeks as world No.1, 92 singles titles, a 1080-227 win-loss record - and just shy of $US135 million ($A201 million) in prize money.

"Really, everything I have experienced has been a dream come true," Nadal said. "I leave with the absolute peace of mind of having given my best, of having made an effort in every way."