The anti-apartheid leader, former South African president and Nobel Peace Prize winner died on Thursday at the age of 95, prompting a vast outpouring of tributes from the world's best-known athletes and top sporting bodies.
Muhammad Ali, himself a role model for so many, said Mandela inspired others to "reach for what appeared to be impossible."
"What I will remember most about Mr. Mandela is that he was a man whose heart, soul and spirit could not be contained or restrained by racial and economic injustices, metal bars or the burden of hate and revenge," Ali said in a statement through his foundation.
Pele wrote, "He was my hero, my friend."
Tiger Woods called his meeting with Mandela in 1998 "inspiring times."
"It's sad for everyone who got a chance to not only meet him, but I've been influenced by him," Woods said.
Usain Bolt posted on Twitter: "One of the greatest human beings ever."
The NBA's LeBron James said: "In his 95 years, he was able to do unbelievable things not only for South Africa but for the whole world."
As much as sportsmen and women loved Mandela, he in turn loved sport and appreciated its enormous potential to do good. Nowhere more than in his own country, where he famously used the 1995 Rugby World Cup to knock down the last barriers of apartheid.
"A remarkable man who understood that sport could build bridges, break down walls, and reveal our common humanity," International Olympic Committee President Thomas Bach said in a statement to The Associated Press. The IOC would fly the Olympic flag at half-staff for three days for Mandela, he said.
Bach later choked up while speaking about when he met Mandela in 1996 and asked the former political prisoner if he felt hatred toward the apartheid regime that imprisoned him for 27 years.
"His immediate response was 'no' but he saw the doubt in my eyes," Bach said on Friday. "'You don't believe me?' he asked. 'I can tell you why. If I hate I would not be a free man anymore.'"
Bach wasn't the only one to show his emotions. Gary Player paused while speaking at a golf tournament in South Africa to compose himself and wipe away tears.
"When you think of a man going to jail for all those years for doing the right thing, not the wrong thing, it's hard to comprehend that a man can come out and be like that," Player said. "He was an exceptional man, just exceptional."
FIFA president Sepp Blatter said he and world football were in mourning at Mandela's passing and ordered that the 209 flags of its member countries at FIFA headquarters in Switzerland also be flown at half-staff.
"It is in deep mourning that I pay my respects to an extraordinary person, probably one of the greatest humanists of our time and a dear friend of mine," Blatter said.
From a cricket test in Australia to basketball games in the United States, and a golf tournament in the wilderness of South Africa, Mandela was remembered by players and fans across sport with moments of silence.
A keen amateur boxer and runner in his youth, Mandela understood the intricacies of rugby, football and cricket, the most popular sports in his country, but even games and players the South African wouldn't have been familiar with were touched by him.
"Nelson Mandela was one of the most powerful and inspirational leaders in the world and a great friend of the NBA," league commissioner David Stern said, "... and while we mourn his passing, we know that his legacy and quest for equality will endure."
Sport was never far from Mandela's mind. He was there — often the driving force — when South Africa returned to the Olympic family, won rugby's World Cup, won football's African Cup and earned the right to host FIFA's World Cup in 2010, the first in Africa. It was fitting that Mandela's last appearance for an adoring public was when he greeted fans in a packed stadium on the outskirts of Soweto ahead of the 2010 World Cup final.
"When he was honoured and cheered by the crowd ... it was as a man of the people, a man of their hearts, and it was one of the most moving moments I have ever experienced," Blatter said.
A string of Spain's World Cup winners from that year and Portugal's Cristiano Ronaldo all tweeted messages of condolence, with many including photographs of themselves with Mandela. Global superstars Woods and David Beckham both made a point of meeting him when they travelled to South Africa. Woods came out of his audience with a copy of the man's autobiography and Beckham was almost reverent in their 2003 meeting.
"We have lost a true gentleman and a courageous human being," Beckham said on his Facebook page. "It was truly an honour to have known a man who had genuine love for so many people."
South African golfer Ernie Els said that from around 1996 onwards Mandela would call him every time he won a tournament and they once exchanged gifts after Mandela visited him at a tournament near the ex-president's Johannesburg home.
"I've still got that picture in my office in the U.S.," Els said. "He was just the most amazing person I have ever met."
But Mandela's interest in sport wasn't just for the grand occasion and the photo opportunity.
Recalling his first conversation with a still imprisoned Mandela in 1986 and away from the media spotlight, former Australian prime minister Malcolm Fraser said Mandela's first question was about cricket and the man regarded as that sport's greatest player.
"His first remark to me, after hello, was ... 'Mr. Fraser, is Donald Bradman still alive?'"
Fraser later brought him a bat signed by Bradman. Cricket's finest batsman had written "in recognition of a great unfinished innings" for Mandela on the bat.
What Mandela did at that 1995 Rugby World Cup final is one of sport's defining moments and enshrined in the new South Africa's conscience.
By pulling on the green and gold jersey of the Springboks, the national team previously all-white and associated with the apartheid regime, Mandela signalled to all South Africans that they should unite. His presentation of the trophy to the Springboks' blond captain Francois Pienaar provided a lasting image of reconciliation that politics just couldn't match.
"It was our privilege to have lived in this country during his lifetime," South African Rugby Union president Oregan Hoskins said. After 1995, Mandela commonly referred to the team that had previously been boycotted abroad for its associations with apartheid as "my beloved Springboks."
Current Springboks captain Jean de Villiers said: "His presence at a test match just lifted the crowd and energized the team — it is actually hard to describe."
Even for New Zealand's losing rugby captain on that famous June day in 1995, Sean Fitzpatrick, Mandela's effect was too momentous not to appreciate.
"Afterwards, when we were driving back to our hotel crying, to see the sheer enjoyment of everyone running down the streets ... black, white, colored, whatever they were, just arm in arm celebrating sport," Fitzpatrick said. "He saw the bigger picture."
Follow Gerald Imray at www.twitter.com/GeraldImrayAP