"I have rassled with an alligator, I have tussled with a whale.
I've handcuffed lightning, thrown thunder in jail.
Only last week I murdered a rock, injured a stone, hospitalized a brick.
I'm so mean I make medicine sick!"

- Muhammad Ali, 1974

The Greatest is gone.

Muhammad Ali, 74, the effervescent heavyweight boxing champion who challenged the U.S. government, became the most recognized face on the planet, and was named top athlete of the 20th century, died Friday of respiratory complications after being in a Phoenix-area hospital for the last few days.

"After a 32-year battle with with Parkinson's disease, Muhammad Ali has passed away at the age of 74. The three-time world heavyweight champion boxer died this evening," family spokesman Bob Gunnell told NBC News.

Mr. Ali's Parkinson's syndrome was diagnosed in 1981, not long after his retirement at age 39. The condition, believed related to the physical punishment of a career in boxing, had progressively slowed his motor skills and slurred his speech.

But during his prime, Mr. Ali's mind, mouth, and moves flashed like lightning. That prime lasted from his gold-medal victory as a skinny 18-year-old at the 1960 Olympics, through his 1964 upset over Sonny Liston to win the world title, through three epic battles with Joe Frazier in the 1970s and two comeback fights to regain the title, against George Foreman and Leon Spinks.

"Ain't never been nothing like me," he boasted, and he was right.

He had the hand speed of a lightweight, the footwork of a dancer, a heavyweight punch, a granite chin, a radar defense, unbridled confidence, and the caginess to outwit stronger opponents.

"Ali was an absolute genius in the ring," said Jim Jacobs, the late boxing historian. "The fastest fighter I've ever seen, live or on film."

Mr. Ali won the heavyweight title three times, defended it 19 times, and closed his 21-year career with a 56-5 record. Sports Illustrated and USA Today were among those to name him the top athlete of the 20th century.

Next to the Rev. Dr. Martin Luther King Jr., Mr. Ali was perhaps the most influential African American of his time. After he joined the Nation of Islam in 1964 and rejected his "slave name" Cassius Clay, Mr. Ali refused to join the Army.

"Why should they ask me to put on a uniform and go 10,000 miles from home and drop bombs and bullets on brown people in Vietnam while so-called Negro people in Louisville are treated like dogs?" he later told Sports Illustrated.

He also, for a time, advocated black separatism and called Christianity the white man's religion.

For avoiding the draft, Mr. Ali was stripped of his title and his license to box, from spring 1967 to fall 1970. He was put under FBI surveillance.

"The man used his athletic ability as a platform . . . taking chances that no one else took," said Jim Brown, the great NFL running back and activist, in Thomas Hauser's book, Muhammad Ali: His Life and Times. "Ali was involved in the Vietnam War . . . in the struggle for racial equality. The Montreal Canadiens, the Green Bay Packers, the New York Yankees, they weren't involved in that. Ali was the most important figure in sports history."

Mr. Ali had audiences with heads of state. He delivered sermons and a Harvard commencement address. He negotiated the release of American hostages in Iraq and hand-delivered medical supplies to orphanages in Africa and Asia. A top-40 pop song about Mr. Ali in 1975 was called "Black Superman."

"Do you have any idea what Ali meant to black people?" baseball Hall of Famer Reggie Jackson once said. "As a young black, at times I was ashamed of my color. I was ashamed of my hair. . . . Do you understand what it did for black Americans to know that the most physically gifted, possibly the most handsome, and one of the most charismatic men in the world was black? The entire experience of being black changed for millions of people because of Ali."

His greatest fight was in Africa, a 1974 upset win over Foreman. It was the $5 million purse, financed by Zaire's violent ruler, Mobutu Sese Seko, that lured Mr. Ali to fight there. But he was welcomed as a folk hero in the country's dirt-road villages and cheered by 100,000 in the arena where he regained the world title.

Mr. Ali also changed the way athletes spoke to the public. He called himself the prettiest, the wittiest - and nicknamed himself "The Greatest." He mocked opponents, predicting knockout rounds, reciting poems.

"If you think the world was shocked when Nixon resigned,
Wait til I kick Foreman's behind."

He was like a stand-up comic when the cameras were on, with a brash media awareness - often egged on by equally loquacious broadcaster Howard Cosell - that set a tone for the self-referential excesses of future athletes.

"People say I'm cocky," Mr. Ali said. "Some say I need a good whuppin'. But anything I say, I'm willing to back up."

Cosell gave his own Ali eulogy of sorts to a TV audience in 1974, believing Ali would lose to Foreman and retire: "Through all of the years, my own memories of him will be as a fighter, and as the strange, and curious, and gregarious, and engaging, and sometimes cruel, and sometimes family man that he is."

Mr. Ali's response, straight into TV cameras: "Howard, you're always talking about how I'm not the same man I was 10 years ago. Well, I just talked to your wife, and she said you're not the same man you were two years ago."

Born in Louisville in 1942 as Cassius Marcellus Clay Jr., Mr. Ali started boxing when he was 12 and almost immediately envisioned himself champion of the world.

"It was like God was telling me that boxing was my responsibility," he once said.

In school he would pretend his name was being announced over the loudspeaker system. "Cassius Clay, heavyweight champion of the world." He never lost that desire for attention.

"Ali never messed with drugs, but he was a junkie for fame," said Drew "Bundini" Brown, an Ali cornerman and confidante.

Mr. Ali played himself in a 1977 movie, The Greatest. (In 2001, actor Will Smith gained 35 pounds of muscle to star in the biographical movie Ali.)

Most of all, though, he was a magnificent boxer. As a teenager, he fought 108 amateur bouts, winning multiple championships by age 18. He won a gold medal at the 1960 Rome Olympics, beating a Polish fighter in the 178-pound final.

It was upon his return from Rome, at the Louisville Airport, that the teenager recited the first of his many boxing poems.

"To make America the greatest is my goal,
So I beat the Russian, and I beat the Pole
And for the USA won the Medal of Gold."

Later he would use poetry to forecast fights.

"Moore in Four."

"The boy likes to mix, so he must fall in six."

Perhaps his most famous limerick, "Float like a butterfly, sting like a bee," was authored by Brown, a street hustler from Harlem who became Mr. Ali's training camp motivator.

Mr. Ali correctly called the round in eight of his first nine pro fights but made fewer predictions as the competition got tougher. He began nicknaming opponents: Liston was the Bear, Foreman the Mummy, Floyd Patterson the Rabbit, Leon Spinks the Vampire.

He wore white shoes with red tassles, dropped his hands daringly to his side in mid-ring, and danced his famous Ali shuffle. At 22, he became the second-youngest man to win the heavyweight title when he upset Liston, as a 7-1 underdog, in 1964.

Disillusioned by racism he saw around him and enthralled by the charismatic Muslim leader Malcolm X, he joined the Nation of Islam and changed his name, first to Cassius X and then Muhammad Ali.

Mr. Ali's controversial 1965 rematch against Liston, held in a converted high-school hockey rink in Lewiston, Maine, saw Liston sag to the canvas and stay down in Round 1 from a "phantom punch" that no one saw, with Mr. Ali shouting: "Get up and fight!"

There were rumors that Liston either was throwing the fight to repay gambling debts or wanted to avoid an assassin who might be out to get Mr. Ali.

In 1966, Mr. Ali announced his intention to avoid the draft for religious reasons. He turned down efforts by his managers to get him easy military duty, entertaining troops.

"Muhammad's actions contributed enormously to the debate about whether the United States should be in Vietnam and galvanized some of his admirers to join protests against the war for the first time," the late Sen. Ted Kennedy said in Hauser's biography.

When his banishment from boxing started in 1967, Mr. Ali was the undefeated world champion, 29-0. By the time the U.S. Supreme Court overturned it, he was more popular than ever - as a martyr and social force.

Although he was just 28 when he returned, the three years away from the ring hurt.

"We never saw him at his peak," said his longtime trainer, Angelo Dundee. "He was still improving, getting bigger and stronger and more experienced in the ring. . . . God only knows how great he would have been."

Mr. Ali spent much of his exile pursuing the man who assumed the heavyweight title in his absence: Joe Frazier, a South Carolina native who made Philadelphia his home as a teenager.

The two fighters warred even when they weren't fighting. Frazier called Mr. Ali by the name Clay and labeled him a draft dodger. Mr. Ali called Frazier an Uncle Tom and The Gorilla.

Descriptions vary of a 1969 incident in which Mr. Ali and Frazier nearly brawled in Philadelphia's Fairmount Park. In a staged confrontation that may or may not have become serious, Mr. Ali went to the Philadelphia gym where Frazier was training - and alerted the media - challenging Frazier to a fight before a gathering mob. Mr. Ali suggested they take it to the park, but Frazier didn't go, according to both boxers' autobiographies.

In 1970, Mr. Ali bought a spacious house on North 72nd Street in Philadelphia's Overbrook section, denying that he was trying to invade Frazier's turf.

"That would be foolish to move into a $73,000 house . . . just to be near someone," he told the Inquirer. "I moved here because it's near New York, and I don't like to fly."

Frazier held a grudge for decades over how Ali vilified him - first as the too-white "Uncle Tom" and then with the ugly racial epithet "gorilla." In his 1996 autobiography, Frazier called Mr. Ali a "mean-spirited egomaniac" and wrote: "I'll open up the graveyard and bury his ass when the Lord chooses to take him."

But in an early 2006 interview with the Inquirer, as Mr. Ali's health faded, Frazier said: "I forgive him. It's up to the Lord now to do the rest of it."

Mr. Ali never fought in Philadelphia. But he bought houses and lived in Cherry Hill twice, in 1971 and 1976. In 1979, he purchased a home in Bala Cynwyd that he didn't live in. He set up a training camp in Deer Lake, Pa., in the Pocono Mountains.

Mr. Ali's comeback fight, in October 1970, was in Atlanta, against Jerry Quarry. Segregationist Georgia governor Lester Maddox desperately tried to stop it. As the fight neared, racial harassment of Mr. Ali peaked when a gift box was delivered to his hotel room in Miami, where he was training. It dripped with blood and contained a chihuahua with its head severed. A note said: "We know how to handle black draft-dodging dogs in Georgia."

The fight went off without incident. A rusty Mr. Ali stopped Quarry on cuts in the third round.

Five months later, Mr. Ali had a chance to regain his title, against Frazier at Madison Square Garden. Ali lost for the first time in 32 pro fights.

But he beat Frazier in their 1974 rematch and finally regained his title that year with the upset over Foreman in Zaire - the "Rumble in the Jungle." Ali outwitted the stronger Foreman, using a peek-a-boo strategy he called the "rope-a-dope," in which he let Foreman punch repeatedly until the big man ran out of gas. Ali knocked Foreman out in Round 8.

Ali and Frazier met a final time in 1975, in the brutal "Thrilla in Manila." Mr. Ali won when Frazier couldn't come out for the 15th round.

Mr. Ali held the title until 1978, when he was upset by Leon Spinks, an Olympic champion from St. Louis who had fought only eight pro bouts.

The day after, Ali went back into training, chanting as he did his roadwork: "Gotta get my title back, gotta get my title back."

He got the title back from Spinks six months later, at age 36, becoming the oldest to win it and the only three-time heavyweight champion.

His final title bout was an ill-advised 1980 match against young champion Larry Holmes. Mr. Ali, medicated and out of shape, had been idle for two years. By then his speech was noticeably slurred, and his reflexes had been slowed by years of punishing blows to his head, liver, and kidneys. Mr. Ali lost every round and endured the beating of his life. The bout was stopped in the 10th round by Dundee, his friend and trainer, who had advised against it.

He fought for the last time in 1981, one month short of his 40th birthday, a 10-round loss to Trevor Berbick.

"Dundee told me, 'Go out and hit him,' " Mr. Ali said afterward. "I said, 'You go out and hit him. I'm tired.' "

Mr. Ali's condition deteriorated, and he was found to have Parkinson's syndrome (not Parkinson's disease, as was sometimes reported). Parkinson's syndrome, which can be caused by physical trauma, is a neurological disorder that causes tremors, rigidity of muscles, and impaired speech and balance.

Mr. Ali spent his middle years shuffling stiffly from place to place, his once-expressive face seemingly frozen, his hands shaking, his once-darting eyes glossed over, his voice reduced to a whisper. But his mind remained sharp, and those closest to him said he enjoyed his retirement years doing what he called "God's work, my real mission in life."

In 1990, when he was 48, he told biographer Hauser: "People say I had a full life, but I ain't dead yet. I'm just getting started. All of my boxing, all of my running around, all of my publicity was just the start of my life.

"Now my life is really starting. Fighting injustice, fighting racism, fighting crime, fighting illiteracy, fighting poverty, using this face the world knows so well and going out and fighting for truth and different causes.

"Talking about boxers bores me now. People today, they want me to talk like I used to. 'I'm the greatest! I'm the prettiest! I'm this, and I'm that.' But I don't want to do that no more. There's bigger work I got to do."

Mr. Ali made some $55 million in the ring, which at the time surpassed the combined earnings of every heavyweight champion before him. But when he retired in 1979, much of the money was gone after bad business deals, taxes, theft, exploitation, and his own generosity. At a dinner in Las Vegas, where past heavyweight champions were honored, each was given a diamond ring worth thousands of dollars. When Mr. Ali left the stage, he passed a little girl in a wheelchair; her mother asked Mr. Ali to pose for a picture. He hugged the girl, kissed her, and left the ring in her hands.

Mr. Ali lost millions in endorsements because of ludicrous "lifetime" contracts he signed in his youth and by giving away thousands of autographs every year. Although he had trustworthy friends, many were along for the ride.

"I saw things done to him that made me sick to my stomach," Dundee said. "And all he'd say was, 'You have to forgive people.' "

In April 2006, CKX, the company that produced American Idol and owned the rights to Elvis Presley merchandising, paid the Ali Trust $50 million for an 80 percent stake in the right to market Ali's name and likeness.

CKX estimated that the "Ali business" had brought in $4 million to $7 million annually in recent years. An Ali-held company called GOAT (for "greatest of all time") retained a 20 percent stake.

In 2013, Authentic Brands Group bought the rights to license Ali-related intellectual property, including his likeness and the phrase "Float like a butterfly, sting like a bee."

The company put a computer- generated likeness of Ali boxing against himself in a Porsche 911 ad campaign and gave him an Instagram page, among other things.

In 1996, a shaky Mr. Ali lit the torch to open the Olympic Games in Atlanta, an emotional scene for a worldwide audience. In November 2005, after receiving the Presidential Medal of Freedom, he attended the opening of the $60 million Muhammad Ali Center in Louisville.

"I wanted more than a building to house my memorabilia," he said. "I wanted a place that would inspire people to be the best that they could be at whatever they chose to do and to encourage them to be respectful of one another."

Mr. Ali remained a devout Muslim until the end. His separatist racial views moderated after the death of Elijah Muhammad, leader of the Nation of Islam, in 1975. Visiting the site of the World Trade Center attacks in 2001, Mr. Ali said: "Rivers, ponds, lakes, and streams - they all have different names. But they all contain water. Just as religions do. They all contain truths. Islam is peace."

Mr. Ali got his faith from his mother, Odessa Grady Clay, a household domestic worker and devout Baptist who took her two sons to church every Sunday.

One of his mother's grandparents, Abe Grady, was an Irishman who came to America from County Clare in the 1860s, and another was the son of a white man and a slave.

Mr. Ali was named for Cassius Marcellus Clay, an abolitionist who had freed his slaves and kept them as employees. Mr. Ali's father, Cassius Sr., a frustrated artist, made a good living in Louisville as a sign painter. Mr. Ali's brother, Rudolph Arnette, who later took the Muslim name Rahaman Ali, had a short career as a pro boxer and later became a member of the Ali entourage.

Mr. Ali had four wives and at least nine children and was an openly unfaithful husband. His first marriage, to Sonji Roi, was annulled after three months. His second wife, Belinda Boyd (later Khalilah Ali), was 17, a devout Muslim chosen by Ali's Muslim brethren. She was the mother of four of his children - Maryum, twins Rasheeda and Jamilla, and Muhammad Jr.

Veronica Porche, a Foreman-Ali poster contest model he met in Zaire, was wife No. 3. She had been his mistress openly, to the embarrassment of Belinda, who left him. Veronica and Ali had daughter Hana before they were married in 1977 and then had Laila, who became a boxing champion herself. Mr. Ali didn't want his daughter to become a boxer, but many of his public appearances in his final years were at her bouts.

Mr. Ali's fourth wife, Lonnie Williams, grew up across the street from the Clay family in Louisville. She was 5 years old when Mr. Ali was making his name as a young pro of 20.

Lonnie and Ali were married on Nov. 9, 1986. They have an adopted son, Asaad. Daughters Miya and Khaliah are by women Ali didn't marry.

"The ladies always loved him," Maryum said in one of his biographies. "I remember one time we were looking at pictures of him when he was young. I said, 'Ooh, Daddy. Ooh, ooh. If you were my age now, I'd go for you.' He looked at me, then he looked at the pictures, and all he said was, 'Yeah, I was pretty.' "

A family spokesman said Mr. Ali's funeral will be open to the public Friday at 2 p.m. at the KFC Yum Center in Louisville. Eulogies will be given by former president Bill Clinton, Billy Crystal, and Bryant Gumbel.

Jay Searcy contributed to this article.