Argentina legend Diego Maradona has died at age 60, his spokesman announced on Wednesday.
The 1986 World Cup-winning captain died of a heart attack at home in Tigre, Argentina, where he was recovering following recent brain surgery.
Argentinian President Alberto Fernandez declared three days of national mourning.
Brazilian great Pele, who Fifa named along with Maradona as the greatest player of the 20th century, mourned the death of his fellow South American on Wednesday.
"Certainly, one day we'll kick a ball together in the sky above," Pele told Reuters.
Argentina and Barcelona captain Lionel Messi paid tribute to his countryman.
"A very sad day for all Argentinians and for football. He has left us but he isn't going anywhere because Diego is eternal. I'll remember the lovely moments I experienced with him and I send my condolences to his family and friends. Rest in peace," he said.
Juventus and Portugal striker Cristiano Ronaldo posted a picture of himself alongside Maradona, with an emotional tribute.
"Today I say goodbye to a friend and the world says goodbye to an eternal genius," Ronaldo said. One of the best ever. An unparalleled magician.
He leaves too soon but leaves a legacy without limits and a void that will never be filled. Rest in peace, ace. You will never be forgotten."
Argentinian news outlet Clarin earlier broke the news, describing the news of Maradona's passing as having a 'worldwide impact'.
Former England striker Gary Lineker said: "By some distance the best player of my generation and arguably the greatest of all time.
"After a blessed but troubled life, hopefully he'll finally find some comfort in the hands of God."
Sheikh Mansoor bin Mohammed bin Rashid, Chairman of the Dubai Sports Council, tweeted that the "world had lost a legend".
Widely regarded as the greatest players of all time, Maradona was heralded as a hero in his homeland for dragging a largely unfancied team all the way to becoming world champions in 1986 when they beat West Germany in the final.
One match in particular at that tournament would forever engrain the bad and the good of Maradona's mercurial yet flawed genius in the collective psyche.
The quarter-final match against England would see the short, barrel-chested Maradona leap like a salmon above Peter Shilton to score the now infamous "Hand of God" goal that left players and fans incandescent.
But they could only marvel at his second, as he set off on a mazy run from inside his own half, eluding half of the England team before slotting past Shilton to score a goal voted by fans as the greatest in World Cup history.
At club level, he broke on to the scene with Buenos Aires' Boca Juniors before playing in Spain with Barcelona.
He was idolised in Italy after guiding unfashionable Napoli to unprecedented Serie A success, winning two titles.
Napoli released a statement saying news of Maradona's passing was a "devastating blow" for both city and club.
"We are in mourning. We feel like a boxer who has been knocked out. We are in shock.
"Always in our hearts. Ciao, Diego."
A mercurial player with almost unfathomable levels of skill, Maradona scored 34 goals in 91 appearances for Argentina, representing them in four World Cups.
Four years after lifting the World Cup in Mexico, he led his country to the 1990 final in Italy, where they were beaten by West Germany.
Maradona captained them again in the US in 1994, but was sent home after failing a drugs test for ephedrine after the first group match against Greece, in which he scored a trademark sublime goal.
During the second half of his career, Maradona struggled with cocaine addiction and was banned for 15 months after testing positive for the drug in 1991.
Years of drug use, overeating and alcoholism truncated his stellar career and he retired from professional football in 1997, on his 37th birthday, during his second stint at Argentinian giants Boca Juniors.
By that time the image of a lithe athlete who could slalom effortlessly through teams had been replaced by a bloated addict who nearly died of cocaine-induced heart failure in 2000.
The Argentina Football Association president said it "shares its deepest pain over the death of our legend, Diego Armando Maradona. You will always be in our hearts".
Ossie Ardiles, a former teammate of Maradona, said on Twitter: "Thank dear Dieguito for your friendship, for your football, sublime, without comparison.
"Simply the best football player in the history of football. So many enjoyable moments together. Impossible to say which one was the best. RIP my dear friend."
Maradona the coach could not quite live up to the lofty standards of Maradona the player.
He coached his national team at the 2010 World Cup, where they suffered a quarter-final exit to Germany.
He was in charge of Gimnasia y Esgrima in Argentina's top flight at the time of his death.