Claim: Muhammad Ali was ranked greatest athlete of the 20th century.

Muhammad Ali -LRB- -LSB- ɑːˈliː -RSB- born Cassius Marcellus Clay Jr. ; January 17 , 1942 -- June 3 , 2016 -RRB- was an American professional boxer and activist . He is widely regarded as one of the most significant and celebrated sports figures of the 20th century . From early in his career , Ali was known as an inspiring , controversial , and polarizing figure both inside and outside the ring .   Cassius Clay was born and raised in Louisville , Kentucky , and began training as an amateur boxer when he was 12 years old . At age 18 , he won a gold medal in the light heavyweight division at the 1960 Summer Olympics in Rome and turned professional later that year . At age 22 in 1964 , he won the WBA , WBC , and lineal heavyweight titles from Sonny Liston in a big upset . Clay then converted to Islam and changed his name from Cassius Clay , which he called his `` slave name '' , to Muhammad Ali . He set an example of racial pride for African Americans and resistance to white domination during the Civil Rights Movement .   In 1966 , two years after winning the heavyweight title , Ali further antagonized the white establishment by refusing to be drafted into the U.S. military , citing his religious beliefs and opposition to American involvement in the Vietnam War . He was eventually arrested , found guilty of draft evasion charges , and stripped of his boxing titles . He successfully appealed the decision to the U.S. Supreme Court , which overturned his conviction in 1971 , by which time he had not fought for nearly four years and thereby lost a period of peak performance as an athlete . Ali 's actions as a conscientious objector to the war made him an icon for the larger counterculture generation .   Ali is regarded as one of the leading heavyweight boxers of the 20th century . He remains the only three-time lineal heavyweight champion , having won the title in 1964 , 1974 , and 1978 . Between February 25 and September 19 , 1964 , Ali reigned as the undisputed heavyweight champion . He is the only boxer to be named The Ring magazine Fighter of the Year six times . He was ranked as the greatest athlete of the 20th century by Sports Illustrated , the Sports Personality of the Century by the BBC , and the third greatest athlete of the 20th century by ESPN SportsCentury . Nicknamed `` The Greatest '' , he was involved in several historic boxing matches . Notable among these were the first Liston fight ; the `` Fight of the Century '' , `` Super Fight II '' , the `` Thrilla in Manila '' versus his rival Joe Frazier , and `` The Rumble in the Jungle '' versus George Foreman .   At a time when most fighters let their managers do the talking , Ali thrived in and indeed craved the spotlight , where he was often provocative and outlandish . He was known for trash talking , and often freestyled with rhyme schemes and spoken word poetry , both for his trash talking in boxing and as political poetry for his activism , anticipating elements of rap and hip hop music . As a musician , Ali recorded two spoken word albums and a rhythm and blues song , and received two Grammy Award nominations . As an actor , he performed in several films and a Broadway musical . Additionally , Ali wrote two autobiographies , one during and one after his boxing career .   As a Muslim , Ali was initially affiliated with Elijah Muhammad 's Nation of Islam -LRB- NOI -RRB- and advocated their black separatist ideology . He later disavowed the NOI , adhering initially to Sunni Islam and later to Sufism , and supporting racial integration , like his former mentor Malcolm X.   After retiring from boxing in 1981 , Ali devoted his life to religious and charitable work . In 1984 , Ali was diagnosed with Parkinson 's syndrome , which his doctors attributed to boxing-related brain injuries . As the condition worsened , Ali made limited public appearances and was cared for by his family until his death on June 3 , 2016 , in Scottsdale , Arizona .