06/04/2016 12:55 EDT

Muhammad Ali Dead Following A Life Of Fighting Opponents In The Ring, And Racism Out Of It

The Greatest.

Muhammad Ali, one of the flashiest, most outspoken athletes and activists of his time, has died at the age of 74.

The celebrated boxer who could "float like a butterfly and sting like a bee" won three world heavyweight titles and an Olympic gold medal during his career. Ali suffered for years from Parkinson's disease, and was hospitalized in Phoenix with respiratory problems earlier this week.

U.S. boxing great Muhammad Ali poses during the Crystal Award ceremony at the World Economic Forum (WEF) in Davos, Switzerland in 2006. (Photo: Andreas Meier/Reuters)

Ali was born Cassius Clay Jr. in Louisville, Ky. in 1942. He was introduced to boxing at the age of 12.

Ali's parents had bought him a bike as a birthday gift, only for it to be stolen later. Ali reported the theft to a policeman named Joe Martin, telling him he planned on beating the thief. Martin told him he had better learn to fight first.

A boxing trainer outside his police work, Martin became Ali's first instructor.

Heavyweight boxer Muhammad Ali trains for his fight against Oscar Bonavena on Dec. 7, 1970 in New York. (Photo:Anwar Hussein/Getty Images)

Ali's first amateur fight in 1954 ended in a split decision.

Two years later, he won the Golden Gloves tournament among novices in the light heavyweight division.

He eventually made it to the U.S. Olympic boxing team, where he fought his way to a light heavyweight gold medal by taking down Polish fighter Zbiginew Pietrzkowski.

Muhammad Ali trains with a speed bag in the early 1960s. (Photo: Robert Riger/Getty Images)

The fight made him a celebrity — Louisville held a victory parade for him upon his return.

But his gold medal didn't mean he could escape the racism of the southern United States, including an incident when a whites-only diner refused to serve him.

But none of it held him back. Ali embarked on a professional career with a challenge against world heavyweight champion Sonny Liston in 1964.

The fight turned Ali into legend. The cocky fighter predicted he would win the fight against Liston who was a decade older, and famously summarized his plan of attack, telling media he would "float like a butterfly, sting like a bee."

Liston dropped out of the fight following the sixth round, after apparently sustaining a shoulder injury. Ali openly declared himself "the greatest."

It was around this time that the fighter joined Muslim group the Nation of Islam and changed his name from Cassius Clay to Muhammad Ali.

"Cassius Clay is a name that white people gave to my slave master," he explained. "Now that I am free, that I don't belong anymore to anyone, that I'm not a slave anymore, I gave back their white name, and I chose a beautiful African one.

After joining the group, Ali created controversy with statements calling for apartheid between black and white people.

Muhammad Ali listens to Elijah Muhammad, the leader of the group Nation of Islam in Philadelphia, Oct. 5, 1963. (Photo: Afro American Newspapers/Gado/Getty Images)

Many admired him for speaking out, as he became a symbol of black pride, refusing to seek the approval of whites.

Ali was stripped of his boxing licence and heavyweight title in 1967, three years after winning it. He refused to fight in the Vietnam War after being drafted, saying he was a Muslim minister, and the war conflicted with his religious beliefs.

Ali was also banned from boxing, fined $10,000, and sentenced to five years in prison. That sentence was overturned three years later.

Muhammad Ali fights Joe Frazier. (Photo: Frank Hurley/NY Daily News Archive via Getty Images)

The year 1970 saw him return to the ring, defeating opponents Oscar Bonavena and Jerry Quarry in knockout bouts.

The following year, he took on Joe Frazier in what was deemed the "Fight of the Century." Ali taunted Frazier as an "Uncle Tom" in the lead-up to the fight.

But Frazier handed Ali his first loss as a professional fighter in the 15th round at Madison Square Garden.

Muhammad Ali lands a left hook knocking out George Foreman during the "Rumble in the Jungle" fight at the Mai 20 Stadium on Oct. 30,1974 in Kinshasa, Zaire. (Photo: The Ring Magazine/Getty Images)

It would all prove a set-up for the "Rumble in the Jungle" in Kinshasa, Zaire, where he had a chance to take the heavyweight title away from favourite George Foreman.

Ali won the fight using a "rope-a-dope" technique that involved leaning against the ropes and averting Foreman's headshots before retaliating with strong rights.

He became a champion once again, in the eighth round.

Muhammad Ali at an event with former opponent Henry Cooper in 1984. (Photo by Doug McKenzie/Hulton Archive/Getty Images)

In 1984, Ali was diagnosed with Parkinson's disease, a condition that affects the nervous system — and has been linked to head trauma he endured during his boxing career.

He nevertheless remained a public figure. In 1990, he met with Iraqi leader Saddam Hussein to negotiate the release of American hostages. In 1996, he lit the cauldron at the opening ceremony of the Summer Olympic Games in Atlanta.

Muhammad Ali lights the Olympic cauldron at the 1996 Summer Games in Atlanta. (Photo: Reuters)

Ali had nine children, including Laila, who became a boxer over her father's objections to women's participation in the sport.

Laila concluded her boxing career with a 24-0 record.

Laila Ali posted a photo of her father with her daughter this week, in response to reports that the former champion was gravely ill after being hospitalized in the Phoenix-area for a respiratory ailment.

With files from The Associated Press

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