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 converting 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.

In 2001, a biographical film, entitled Ali, was made, with Will Smith starring as Ali. The film received mixed reviews, with the positives generally attributed to the acting, as Smith and supporting actor Jon Voight earned Academy Award nominations. Prior to making the Ali movie, Will Smith had continually rejected the role of Ali until Muhammad Ali personally requested that he accept the role. According to Smith, the first thing Ali said about the subject to Smith was: "You ain't pretty enough to play me."

On November 17, 2002, Muhammad Ali went to Afghanistan as "U.N. Messenger of Peace". He was in Kabul for a three-day goodwill mission as a special guest of the United Nations.

He received the Presidential Medal of Freedom at a White House ceremony on November 9, 2005, and the "Otto Hahn peace medal in Gold" of the United Nations Association of Germany (DGVN) in Berlin for his work with the US civil rights movement and the United Nations (December 17, 2005).

On November 19, 2005 (Ali's 19th wedding anniversary), the $60 million non-profit Muhammad Ali Center opened in downtown Louisville. In addition to displaying his boxing memorabilia, the center focuses on core themes of peace, social responsibility, respect, and personal growth.

In personal life Muhammad Ali has been married four times and has seven daughters and two sons.

Source : www.wikipedia.org