Muhammad Ali (born Cassius Marcellus Clay Jr. on January 17, 1942) is a retired American boxer and former three-time World Heavyweight Champion. To date, he remains the only man to have won the linear heavyweight championship three times (the linear title is recognized by tracing an - almost - unbroken lineage of titleholders going back over 100 years, with nearly every champion defeating the previous titleholder in the ring). Ali was also the winner of an Olympic Light-heavyweight gold medal. In 1999, Ali was crowned "Sportsman of the Century" by Sports Illustrated and the BBC.

Cassius Marcellus Clay, Jr., was born in Louisville, Kentucky. He was named after his father, Cassius Marcellus Clay Sr., who was named for the 19th century abolitionist and politician Cassius Clay. Ali changed his name after joining the Nation of Islam in 1964, subsequently converted to Sunni Islam in 1975 and then Sufism.

Ali was known for his fighting style, which he described as "Float like a butterfly, sting like a bee". Throughout his career Ali made a name for himself with great handspeed, as well as swift feet and taunting tactics. While Ali was renowned for his fast, sharp out-fighting style, he also had a great chin, and displayed great courage and an ability to take a punch throughout his career.