Muhammad Ali, the charismatic three-time heavyweight boxing champion of the world, who declared himself “the greatest” and proved it with his fists, the force of his personality and his magnetic charisma, and who transcended the world of sports to become a symbol of the antiwar movement of the 1960s and a global ambassador for cross-cultural understanding, died June 3 at a hospital in Scottsdale, Ariz., where he was living. He was 74.<br /> His family released a statement confirming his death. The boxer had been hospitalized with respiratory problems related to Parkinson’s disease, which had been diagnosed in the 1980s.Mr. Ali dominated boxing in the 1960s and 1970s and held the heavyweight title three times. His fights were among the most memorable and spectacular in history, but he quickly became at least as well known for his colorful personality, his showy antics in the ring. Cassius Marcellus Clay Jr. was born Jan. 17, 1942, in Louisville. His father was a sign-painter, and his mother was a domestic houseworker.Mr. Ali played few sports as a child, but he began boxing at age 12 to exact revenge on a thief who had stolen his bicycle. He quickly became enamored of the sport, and he won several national amateur boxing championships before he graduated from high school in 1960.