Muhammad Ali. (Photo/CCTV.com)

Boxing legend Muhammad Ali died on Friday, a family spokesman said in a statement.

"After a 32-year battle with Parkinson's disease, Muhammad Ali has passed away at the age of 74," spokesman Bob Gunnell said.

Ali, one of the world's most celebrated athletes, was hospitalized this week for a respiratory ailment in Phoenix area. The family spokesman has said he was in fair condition, but speculation has swirled about his health.

Ali has suffered from Parkinson's disease for more than three decades and has kept a low profile in recent years.

Ali's last public appearance was in April at the "Celebrity Fight Night" gala in Arizona, a charity that benefits the Muhammad Ali Parkinson Center.

At the height of his career, Ali was known for his dancing feet and quick fists and his ability, as he put it, to float like a butterfly and sting like a bee.

Nicknamed "The Greatest," he retired from boxing in 1981 with a 56-5 record. Ali's diagnosis of Parkinson's came about three years after he retired.

Ali, born in Louisville, Kentucky, as Cassius Marcellus Clay Jr., changed his name in 1964 after his conversion to Islam.