There has been an outpouring of tributes to boxing legend Muhammad Ali, who died on June after a lengthy battle with Parkinson's disease. He was 74.
Ali's died one day after he was admitted to a Phoenix-area hospital with a respiratory ailment.
A family spokesman said he died of septic shock "due to unspecified natural causes."
A public funeral procession and memorial service will take place in his hometown of Louisville, Kentucky, on June 10.
His record-setting boxing career, unprecedented flair for showmanship, and controversial stands made Ali one of the best-known figures of the 20th century.
Tributes for the heavyweight great poured in from across the world.
In the United States, President Barack Obama described Ali as a towering champion "who fought for what was right."
Obama said that even as Ali's physical powers were in decline, the boxing great "became an even more powerful force for peace and reconciliation around the world."
"A part of me slipped away, the greatest piece," George Foreman, a former heavyweight champion boxer and one of Ali's most formidable opponents in the ring, said on Twitter.
American civil rights campaigner Jesse Jackson said Ali had been willing to sacrifice the crown and money for his principles when he refused to serve in the Vietnam War.
Front-running Democratic presidential candidate Hillary Clinton remembered Ali by including a shot at the presumptive Republican nominee, Donald Trump.
Clinton said the U.S. is a country "where people can break down barriers, where they can worship their own God, where they can choose their own name [as Ali did]."
Trump wrote in a tweet that Ali is "a truly great champion and a wonderful guy. He will be missed by all!"
Ali had earlier spoken against Trump's proposal to ban Muslims from entering the United States due to perceived terrorist threats.
Democratic candidate Bernie Sanders said that Ali "is, you know, what a hero, what a great man and I say to all the people who are intimidated, and I've been all over the country and talk to Muslim people who say, 'You know, Bernie, our kids are now afraid,'" he said, in a jab at Trump. "I say to those people, one of the great American heroes in modern history was the great Muhammad Ali, a very proud Muslim."
Nicknamed "the Greatest," he was the first person to win the heavyweight championship three times.
But there is more to the boxing legend than just the knockouts he dealt opponents over his 20-year professional career.
A showman, civil rights campaigner, militant who spoke boldly against racism in the 1960s as well as the Vietnam War, and converted Muslim, Ali was arguably the most charismatic sportsman of his time.
Ali's diagnosis of Parkinson's came about three years after he retired from boxing in 1981.
During and after his championship reign, Ali met scores of world leaders and for a time he was considered the most recognizable person on earth.
Muhammad Ali was born Cassius Marcellus Clay Jr on 17 January 1942 in Louisville.
He began to box at the age of 12 and by 18 he had won the gold medal at the Rome Olympics in 1960.
A string of impressive victories coupled with his brash, self-promoting style -- which included taunting his opponents in his unique lyrical way -- won the 1.91-meter Ali fame.
In 1964, he beat Sonny Liston, becoming the world's heavyweight champion for the first time at 22.
Ahead of the fight, he declared: “I’m young, I’m handsome, I’m fast, I’m pretty, and can’t possibly be beaten,” while repeatedly calling Liston "the big ugly bear," among other things.
Ali was also active outside the ring, becoming a symbol of black liberation and civil rights. His sometimes controversial actions won him both admirers and critics.
He changed his name in the mid-1960s when he converted to Islam, explaining that Cassius Clay was the name a white master gave to slaves and he wanted to choose a "beautiful African name."
He also joined the Nation of Islam, a mainly African-American movement which called for black development outside the majority white society.
And he refused to be drafted into the army at a time the United States was fighting in Vietnam.
As Ali put it, “I just don't think I should go 10,000 miles from here and shoot some black people (eds: Vietnamese) who never called me 'nigger,' never lynched me, never put dogs on me, never raped my mama, enslaved me, and deprived me of freedom, justice, and equality.”
For that Ali paid dearly. He was stripped of his world title and sentenced to five years in jail, although the jail term was later dropped on appeal. The cruelest blow, however, was that Ali was banned from boxing for more than three years.
Ali returned to the ring in 1970 and a year later squared off against world champion Joe Frazier in what was dubbed "The Fight of the Century." Ali, however, lost the 15-round battle, his first professional loss.
In 1974, Ali defeated Foreman in Zaire (now called the Democratic Republic of Congo) in the so-called "Rumble in the Jungle." In an epic eighth-round knockout, Ali regained at 32 the championship he had won a decade earlier.
"I told you today I'm still the greatest of all times,” he said after the fight. “Never again defeat me; never again say that I'm going to be defeated; never again make me the underdog until I'm about 50 years old. Then you might get me."
Ali and Frazier squared off for a third and final time in 1975 in the Philippines. Ali defended his title in a brutal 15-round battle called "The Thrilla in Manila."
In 1978, Ali lost his title to Leon Spinks, a man 12 years younger. However, Ali won the title back later that year for a third time. He was 36.
He eventually retired in 1981. Over 20 years, Ali had won 56 fights, 37 by knockout. He lost only five times.
However, Ali was still to face his toughest opponent ever: Parkinson's disease, which he was diagnosed with in 1984. The disease has been linked to head trauma from sports like boxing. The condition's trademark trembling became all too apparent in 1996 when Ali lit the Olympic flame in Atlanta.
Although the neurological affliction slowly robbed Ali of both physical coordination and speech, he remained active, devoting himself to various causes.
In 1991, on the eve of the U.S. Gulf War, he met with Iraqi leader Saddam Hussein to help negotiate the release of American hostages in Baghdad.
Twenty years later, in May 2011, the boxing legend was involved in efforts to free two American hikers held captive in Iran for nearly two years -- Shane Bauer and Josh Fattal.
A letter to Supreme Leader Ayatollah Ali Khamenei was read at the National Press Club in Washington in Ali’s presence.
Speaking on his behalf, his wife Lonnie said, “Regardless of how things are going between the Republic of Iran and the United States, the people of Iran are good people -- they’re good people in their heart -- and I can assure you they love [Muhammad Ali]. It’s based on that compassion [and] for the love of Allah and the love of [Prophet] Muhammad that we ask for their release.”
In January, Washington Post journalist Jason Rezaian was released from an Iranian prison after intervention by Ali.
Rezaian said that when he heard Ali called for his release it was a "turning point" for him.
Rezaian wrote in a Washington Post column on June 4 that knowing Ali publicly acknowledged him was "everything to me."
Rezaian was arrested in July 2014 and was jailed until January when he was released as part of a U.S.-Iran prisoner exchange.
Iranian officials never said why Rezaian was arrested. He said he learned of Ali's comments while imprisoned.
Rezaian wrote that since Ali is revered by Iranians, several prison guards began treating him with more respect.
Ali also was a spokesman for religious tolerance.
Asked in an interview how he balanced his belief in being “the greatest” with his humility as a Muslim, Ali responded in typical style: “Allah is the greatest. I'm just the greatest boxer.”
With reporting by Reuters, AP, and AFP