Muhammad Ali , who was renowned as much for his wit and principles as his fighting prowess, died Friday night at age 74, a family spokesman said.

The boxing legend popularly known as The Greatest died at a hospital in Arizona, where he had been treated for respiratory issues. "After a 32-year battle with Parkinson's disease, Muhammad Ali has passed away at the age of 74," spokesman Bob Gunnell said in a statement. He said the funeral would be in Louisville, Kentucky, Ali's hometown.

The cause of death was septic shock from unspecified natural causes, Reuters reported Saturday.

Ali was regarded as one of the most charismatic people of his generation. Through his athletic skills, braggadocio and defiance of the government, Ali piled up victories, fans and critics.

He was the first boxer to win the world heavyweight title three times, retiring in 1981 with a record of 56-5, with 37 knockouts . In 1999, he was named Sportsman of the Century by Sports Illustrated and Sports Personality of the Century by the BBC. Time once referred to him as the "best-known person on the planet."

But he also spent much of his illustrious career shadowed by controversy. As his fame grew, Ali joined the black separatist group Nation of Islam , changing his name from Cassius Clay. He was then forced to sit out several of the prime years of his career for refusing to join the U.S. Army during the Vietnam War.

After his boxing days ended, Ali immersed himself in philanthropy as he dealt with the onset and advance of Parkinson's syndrome.