Muhammad Ali, heavyweight champion boxer, humanitarian and civil rights icon, has died at age 74. Ali died Friday (June 3) at a Phoenix-area hospital, after spending the past few days being treated for respiratory complications, a family spokesman told NBC News.

Ali was an iconic figure with a quick wit and defiant persona who'd come to the fore in the early 1960s as Cassius Clay, a brash and confident young challenger to then-heavyweight champ Sonny Liston.

Ali was born Cassius Marcellus Clay on January 17, 1942 in Louisville, Kentucky, to middle-class parents. From the age of 12, he showed proficiency in boxing; winning Golden Gloves titles up through age 18, when he won a gold medal as a light heavyweight at the 1960 Olympics in Rome.

After he turned professional, he became famous for his cocky demeanor and clever, braggadocios self-promotion.He teamed with legendary trainer Angelo Dundee and began working towards the heavyweight title. A staunch opponent of American racism, Ali had begun a conversion to Islam after being inspired by Malcolm X, and had already quietly converted prior to his fight with Liston in 1964.

With the world eager for the showdown in Miami Beach, Clay declared that he would "float like a butterfly, sting like a bee," and the younger fighter defeated Liston in a sixth-round technical knockout; proclaiming from the ring: "I am the greatest! I am the greatest! I shook up the world! I'm the king of the world!"

At 22, he renounced "Cassius Clay" as his "slave name" and publicly emerged as Muhammad Ali. In the early 1960s, with a stigma against the Nation of Islam amongst many Americans, it was a bold move. But it would be one of several the champ would embrace.

After successfully defending his title, (including an infamous 1967 bout against Ernie Terrell when Ali pummeled Terrell and screamed "What's my name?" in the eighth round after the challenger had repeatedly called him "Cassius Clay" in interviews), Ali was drafted to serve in the U.S. Army. With the Vietnam War raging, Ali refused to serve. "My conscience won't let me go shoot my brother, or some darker people, some poor, hungry people in the mud, for big powerful America, and shoot them for what?" Ali said. "They never called me 'nigger.' They never lynched me. They didn't put no dogs on me." When he was subsequently stripped of his boxing title and banned from the sport, (following a conviction for draft evasion and appealed prison sentence) Ali spent his time lecturing about racism and American hypocrisy regarding the war.

His appeal reached the U.S. Supreme Court in 1971 and that June, his conviction was reversed in a unanimous decision. He'd been granted a boxing license by the state of Georgia and he fought and beat Jerry Quarry. Six months later, Ali lost to Joe Frazier in a 15-round fight at a sold-out Madison Square Garden--the first time Ali was defeated as a pro. That fight initiated one of the greatest rivalries the sport has ever seen, and Ali and Frazier would face off again in 1974, with Ali emerging victorious.

That set up a bout against heavyweight champion George Foreman later in the year. Hyped as "The Rumble in the Jungle," the fight took place in Zaire and saw Ali moving to Africa and being embraced by the people--who would follow him as he trained, chanting "Ali Bomaye! ("Ali, kill him!" in Lingala). With the backdrop of a three day music festival and Ali's own charismatic charming of the country, the fighter would deliver one of his most iconic fights, employing a strategy dubbed the "rope-a-dope," where he provoked Foreman into attacking him repeatedly while Ali only defended himself. Once Foreman became tired, Ali aggressively counterattacked and knocked the champ out in the eighth round and reclaiming the title.

He fought Frazier a final time in 1975, in a fight dubbed the "Thrilla in Manila." Ali won in a technical knockout in the 15th round. He would retain the title until 1978, when he was defeated by Leon Spinks. He won it back, before retiring in 1979. He returned to the ring in 1980 to face Larry Holmes in a title match that Ali lost. He lost to Trevor Berbick the following year and finally walked away from the sport permanently.

"I'm in no pain," he told The New York Times after it was made public that he was suffering from Parkinson's Disease in 1981. "A slight slurring of my speech, a little tremor. Nothing critical. If I was in perfect health — if I had won my last two fights — if I had no problem, people would be afraid of me. Now they feel sorry for me. They thought I was Superman. Now they can go, 'He's human, like us. He has problems.'"

Even as his health declined, Ali would become a highly visible ambassador and humanitarian, traveling to Lebanon in 1985 and Iraq in 1990 to seek the release of American hostages. In 1996, he lit the Olympic flame in Atlanta, and that same year, the docu-film When We Were Kings, about "The Rumble In the Jungle," was released in theaters with a soundtrack that included a hip-hop track called "Rumble In the Jungle" featuring The Fugees and A Tribe Called Quest. In 2005, President George W. Bush honored Ali with the Presidential Medal of Freedom. The Muhammad Ali Center opened that year in his hometown of Louisville. He also became a public advocate for sufferers of Parkinson's disease and for the Islamic community in America and worldwide.

Following Donald Trump's anti-Muslim rhetoric in the wake of the San Bernadino shooting, Ali addressed violence and hatespeech.

“We as Muslims have to stand up to those who use Islam to advance their own personal agenda,” Ali wrote. “They have alienated many from learning about Islam. True Muslims know or should know that it goes against our religion to try and force Islam on anybody.”

“Speaking as someone who has never been accused of political correctness, I believe that our political leaders should use their position to bring understanding about the religion of Islam and clarify that these misguided murderers have perverted people’s views on what Islam really is,” he said.

“I am a Muslim and there is nothing Islamic about killing innocent people in Paris, San Bernardino, or anywhere else in the world. True Muslims know that the ruthless violence of so called Islamic Jihadists goes against the very tenets of our religion.”

The greatest of all time, Ali's death sparked an outpouring of grief and gratitude for the icon. NBA legend and fellow Muslim Kareem Abdul Jabbar summed up Ali's legacy as a hero to African Americans, in particular.

"To the African-American community, he was a black man who faced overwhelming bigotry the way he faced every opponent in the ring: fearlessly," wrote Jabbar on Facebook.

R.I.P. to the Champ.

Check out some of the celebrity tributes from social media below:




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