The life of Nelson Mandela is being celebrated at the FNB Stadium in Soweto, where the former South African president made his last public appearance at the stadium at the closing ceremony of the 2010 football World Cup.
More than 60 heads of state are attending the day of speeches, music and celebration.
Follow our live updates below.
Mandela's body will lie in state at South Africa's seat of government, the Union Buildings in Pretoria, until he is laid to rest in a state funeral at his home town of Qunu in the Eastern Cape on Sunday.
The Prince of Wales will be among a smaller number of dignitaries travelling to the remote rural location for that service.
Here's a more in-depth report, from my colleague Tom Moseley, on Zuma's difficult day.
More boos for Zuma at FNB Stadium. As South Africa buries Titan of ANC, crisis for his successor - and the Party - never greater. #Mandela— Jon Williams (@WilliamsJon) December 10, 2013
"We sing he is one of a kind, there is no one quite like him," he says.
"The song is one of the most accurate descriptions of the global icon."
During apartheid and Mandela's imprisonment "we stared into the heart of darkness", Zuma says, but Mandela steered the country away from civil war.
"There is no one like Madiba. He was one of a kind."
This is humiliating for South Africa's president, who has had to have music played before his speech - to drown out the boos.
Zuma's reception will be interesting. The crowd was kinder to De Klerk than they were to him— Gary Younge (@garyyounge) December 10, 2013
Apparently Jacob Zuma will 'keep things brief'. Given boos earlier, maybe wise.— Paul Waugh (@paulwaugh) December 10, 2013
Cuba's president, the brother of Cuban revolutionary Fidel Castro, has been diplomatic in his speech, speaking only of praise for the man Mandela and "the heroic people of South Africa".
Mandela led a nation "bent on overcoming the consequences of colonialism, slavery and racial segregation" Castro says.
Cuba's "children have African blood in their veins," he said, speaking of the close bond between the two nations.
"Nelson Mandela will go down in history because he was capable of cleaning his soul of poison."
"The man who wanted to take you on the first stage of the journey is not necessarily the man to take you on the next stage, he [Mandela] was happy to pass over to other people."
We've now heard tribute from Brazil's president Dilma Rousseff, Vice-President Li Yuanchao of China and President Hifikepunye Pohamba of Namibia.
President Pranab Mukherjee of India began his speech as a band played and had to be stopped by Ramaphosa, who sought out the band to stop the noise.
Mukherjee said that Indians view Mandela as a "venerated elder, a great soul" in the mould of Mahatma Gandhi, because of his commitment to non-violence and dignity.
He said Mandela's lesson is that "nothing is impossible. That even the greatest injustices in the world can be overcome.
"You’ve got to bring together people of good will and you’ve got to show courage.
"No prison cell, no threat of death, no torture could stop him pursuing the dream that we’d have a multi-racial South Africa."
First Castro and Obama, now the old French rivals President Francois Hollande high-fives former French President Nicolas Sarkozy.
Obama's speech has been widely praised by Americans on social media, with several calling it the best speech of his Presidency.
Could well be best speech of Obama's presidency. #Mandela— ian bremmer (@ianbremmer) December 10, 2013
This speech may be remembered as one of the best of Obama's presidency. Eulogies are his strength, but this is bigger than Tucson, others.— Jeff Zeleny (@jeffzeleny) December 10, 2013
Obama is giving his best speech as a statesman. I am impressed.— Bill Buster (@ActorBuster) December 10, 2013
The best Obama speech i've heard in a while. Skillfully pointing fingers at wannabe dictators using Mandelas ideals as their "moral" centre.— Michael Lowman (@michael_lowman) December 10, 2013
Even in death, Mandela showed his power to unite people. This was quite an extraordinary moment between the two nations, hostile for half a century.
Barack Obama did not just given Raul Castro a quick handshake, but bent down and spoke briefly to him.
Obama spoke a few moments later of "Ubuntu", which he called Mandela's "greatest gift: his recognition that we are all bound together in ways that can be invisible to the eye; that there is a oneness to humanity; that we achieve ourselves by sharing ourselves with others, and caring for those around us."
Something he perhaps had in mind as he approached Cuba's president.
Winnie Madikizela-Mandela, Nelson Mandela's former wife, looks deep in grief as the speeches go on around her.
All together again, John Major, centre, greets George W. Bush as Bill Clinton pokes his fellow ex-president
"We will never see the likes of Nelson Mandela again," Obama says.
"But let me say to the young people of Africa, and young people around the world - you can make his life’s work your own.
"After this great liberator is laid to rest; when we have returned to our cities and villages, and rejoined our daily routines, let us search then for his strength - for his largeness of spirit - somewhere inside ourselves.
"And when the night grows dark, when injustice weighs heavy on our hearts, or our best laid plans seem beyond our reach - think of Madiba, and the words that brought him comfort within the four walls of a cell:
"'It matters not how strait the gate, How charged with punishments the scroll, I am the master of my fate, I am the captain of my soul.'
George W Bush is looking like he's in a right grump, watching Obama's speech.
Obama is giving a not-so-sly dig at other politicians, not just in his own country, but at some of the world leaders seated in the stadium.
"We cannot allow our progress to cloud the fact that our work is not done," he says.
"The struggles that follow the victory of formal equality and universal franchise may not be as filled with drama and moral clarity as those that came before, but they are no less important."
Children are still starving, schools are run down, "men and women are still imprisoned for their political beliefs; and are still persecuted for what they look like, or how they worship, or who they love.
"There are too many of us who happily embrace Madiba’s legacy of racial reconciliation, but passionately resist even modest reforms that would challenge chronic poverty and growing inequality.
"There are too many leaders who claim solidarity with Madiba’s struggle for freedom, but do not tolerate dissent from their own people.
"And there are too many of us who stand on the sidelines, comfortable in complacency or cynicism when our voices must be heard."
Obama says Mandela embodies "Ubuntu" a South African value which means "that there is a oneness to humanity".
"We remember the gestures, large and small - introducing his jailors as honored guests at his inauguration; taking the pitch in a Springbok uniform; turning his family’s heartbreak into a call to confront HIV/AIDS - that revealed the depth of his empathy and understanding.
"He not only embodied Ubuntu; he taught millions to find that truth within themselves.
"It took a man like Madiba to free not just the prisoner, but the jailor as well; to show that you must trust others so that they may trust you; to teach that reconciliation is not a matter of ignoring a cruel past, but a means of confronting it with inclusion, generosity and truth.
"He changed laws, but also hearts."
"He was not a bust made of marble; he was a man of flesh and blood - a son and husband, a father and a friend," says Obama
"He tells us what’s possible not just in the pages of dusty history books, but in our own lives as well."
Obama compares Mandela to the world's greatest heroes and peacemakers - and America's greatest presidents.
"Like Gandhi, he would lead a resistance movement - a movement that at its start held little prospect of success.
"Like King, he would give potent voice to the claims of the oppressed, and the moral necessity of racial justice.
"He would endure a brutal imprisonment that began in the time of Kennedy and Khrushchev, and reached the final days of the Cold War.
"Emerging from prison, without force of arms, he would - like Lincoln - hold his country together when it threatened to break apart.
"Like America’s founding fathers, he would erect a constitutional order to preserve freedom for future generations - a commitment to democracy and rule of law ratified not only by his election, but by his willingness to step down from power."
It is "tempting then to remember Nelson Mandela as an icon, smiling and serene, detached from the tawdry affairs of lesser men," Obama says.
"Madiba himself strongly resisted such a lifeless portrait." he continues, to wild applause.
Mandela's strength was "sharing with us his doubts and fears; his miscalculations along with his victories".
Wide shots of the stadium show a good number of empty orange seats.
There's also some problems with the public address system, and the crowd has voiced their disapproval, during the speech of the AUC's Nkosazana Dlamini-Zuma.
Nkosazana Dlamini-Zuma almost inaudible due to mediocre sound system and a restless, noisy crowd. Rain getting heavier too.— David Smith (@SmithInAfrica) December 10, 2013
"It is a singular honor to be with you today, to celebrate a life unlike any other," Obama says as he takes the stage to rapturous applause.
He's better at projecting his voice than a few of the other speakers..
The US President will speak in the next few minutes.
Barack Obama got the biggest cheer of the day so far when his picture appeared on the big screen, with South Africa's jacob Zuma getting the biggest boo.
Other reactions were missed. Some boos rang out as the camera panned momentarily across the face of former US President George W Bush.
And the reaction was mixed for Zimbabwe's Robert Mugabe, who invoked a visceral reaction of boos, but also cheering from the crowd.
Palestinian leader Mahmoud Abbas received a cheer from the crowd, as did Bill Clinton.
The former US President arrived late to the ceremony, pausing by the British political delegation to chat to Nick Clegg, of all people.
Security experts told South Africa's Times newspaper that Mandela's memorial service and funeral would be managed "by the second" to avoid diplomatic embarrassment. They "can be seated alphabetically to avoid Robert Mugabe sitting next to David Cameron; and Raul Castro Ruz sitting next to Barack Obama."
"What a wondrous display of this rainbow nation," says the UN Secretary-General.
"South Africa has lost a hero, a father.
"The world has lost a beloved friend and mentor. Mandela was more than one of the greatest leaders of all time.
Remember, you can get all the atmosphere, and watch the speeches right here on the LIVESTREAM.
He's with his wife Michelle, and will be the first of the world leaders to pay tribute to Mandela later in the proceedings
As General Thanduxolo Mandela and the grandchildren of the former President get up to speak, the crowd boos even more vociferously, as an image of Zuma appears on the big screen.
Two things the director should avoid - showing Mbeki on the screen and showing Zuma on the screen for our sake.— Khaya Dlanga (@khayadlanga) December 10, 2013
Zuma is scheduled to give the closing keynote speech. It will be interesting to see how that is received by this exceptionally anti-Zuma crowd.
The death of Mandela has been a not unwelcome distraction for Zuma, who has faced repeated calls for his resignation after he was challenged by the country's security watchdog for spending $20m on security for his personal home - reportedly including a swimming pool and cattle facilities.
Zuma will lead the ANC into elections next year.
"He was an inspiration to billions by epitomising the values of sacrifice and patience. He created hope when was none," said the 87-year-old, his voice breaking with emotion.
Mlangeni was an ANC stalwart, with Mandela and did military training abroad. He was sentenced to life imprisonment on Robben Island.
"Madiba is looking down on us. There is no doubt he is smiling and he watches his beloved country, men and women, unite to celebrate his life and legacy," Mlangeni told the crowd.
South Africa's president was not given a warm welcome in the Soweto stadium by the crowds, with audible boos ringing out in the rain.
Nevertheless, the boo-ing was widely condemned by South Africans on social media.
It was disrespectful of the people at Soccer City to boo pres Zuma, they didn't come for Zuma, this is Tata Madiba's memorial. #Disappointed— #RIPTata™ (@BigWizReloaded) December 10, 2013
We need to boo Zuma during the elections using our loudest voice-the vote. NOT at a funeral of a world icon— Portia De Nosy (@MissySparklez) December 10, 2013