Muhammad Ali (; born Cassius Marcellus Clay Jr.; January 17, 1942 June 3, 2016) was an American professional boxer and activist. Nicknamed "The Greatest", he is widely regarded as one of the most significant and celebrated sports figures of the 20th century, and is frequently ranked as the greatest heavyweight boxer of all time. In 1999, he was named Sportsman of the Century by Sports Illustrated and the Sports Personality of the Century by the BBC.

Born and raised in Louisville, Kentucky, he began training as an amateur boxer at age 12. At 18, he won a gold medal in the light heavyweight division at the 1960 Summer Olympics and turned professional later that year. He became a Muslim after 1961. He won the world heavyweight championship from Sonny Liston in a major upset on February 25, 1964, at age 22. Also that year, he renounced his birth name as a "slave name" and formally changed his name to Muhammad Ali. In 1966, Ali refused to be drafted into the military owing to his religious beliefs and ethical opposition to the Vietnam War and was found guilty of draft evasion and stripped of his boxing titles. He stayed out of prison while appealing the decision to the Supreme Court, where his conviction was overturned in 1971. However, he had not fought for nearly four years by this point and had lost a period of peak performance as an athlete. Ali's actions as a conscientious objector to the Vietnam War made him an icon for the larger 1960s counterculture generation, and he was a very high-profile figure of racial pride for African Americans during the civil rights movement and throughout his career. As a Muslim, Ali was initially affiliated with Elijah Muhammad's Nation of Islam (NOI). He later disavowed the NOI, adhering to Sunni Islam, and supported racial integration like his former mentor Malcolm X.

He fought in several historic boxing matches, such as his highly publicized fights with Sonny Liston, Joe Frazier (including the Fight of the Century, the biggest boxing event up until then), the Thrilla in Manila, and his fight with George Foreman The Rumble in the Jungle. Ali thrived in the spotlight at a time when many boxers let their managers do the talking, and he became renowned for his provocative and outlandish persona. He was famous for trash-talking, often free-styled with rhyme schemes and spoken word poetry incorporating elements of hip hop, and often predicted in which round he would knockout his opponent.

Outside boxing, Ali attained success as a spoken word artist, releasing two studio albums: I Am the Greatest! (1963) and The Adventures of Ali and His Gang vs. Mr. Tooth Decay (1976). Both albums received Grammy Award nominations. He also featured as an actor and writer, releasing two autobiographies. Ali retired from boxing in 1981 and focused on religion, philanthropy and activism. In 1984, he made public his diagnosis of Parkinson's syndrome, which some reports attributed to boxing-related injuries, though he and his specialist physicians disputed this. He remained an active public figure globally, but in his later years made fewer public appearances as his condition worsened, and he was cared for by his family. Ali died on June 3, 2016.

The Nation of Islam (NOI) is a religious and political organization founded in the United States by Wallace Fard Muhammad in 1930.

A black nationalist organization, the NOI focuses its attention on the African diaspora, especially on African Americans. While it identifies itself as promoting a form of Islam, its beliefs differ considerably from mainstream Islamic traditions. Scholars of religion characterise it as a new religious movement and a UFO religion. It operates as a centralized and hierarchical organization. Its critics, including the Southern Poverty Law Center and the Anti-Defamation League, have accused it of being a black supremacist hate group that promotes racial prejudice towards white people, anti-semitism, and anti-LGBT rhetoric. Muslim critics accuse it of promoting teachings that are not legitimately Islamic.

The Nation teaches that there have been a succession of mortal gods, each a black man named Allah, of which Fard Muhammad is the most recent. It claims that the first Allah created the earliest humans, the Arabic-speaking, dark-skinned Tribe of Shabazz, whose members possessed inner divinity and from whom all people of color are descended. It maintains that a scientist named Yakub then created the white race. The whites lacked inner divinity and were intrinsically violent; they overthrew the Tribe of Shabazz and achieved global dominance. Setting itself against the white-dominated society of the United States, the NOI campaigns for the creation of an independent African American nation-state and calls for African Americans to be economically self-sufficient and separatist. A millenarian tradition, it maintains that Fard Muhammad will soon arrive aboard a spaceship, the "Mother Plane" or "Mother Ship," to wipe out the white race and establish a utopia. Members worship in buildings called mosques or temples; their beliefs are materialist, rejecting the existence of any spiritual essence or afterlife. Practitioners are expected to live highly disciplined lives, adhering to strict dress codes, specific dietary requirements, and patriarchal gender roles.

Wallace Fard Muhammad established the Nation of Islam in Detroit. He drew on various sources, including Noble Drew Ali's Moorish Science Temple of America, black nationalist trends like Garveyism, and black-oriented forms of Freemasonry. After Fard Muhammad disappeared in 1934, the leadership of the NOI was assumed by Elijah Muhammad. He expanded the NOI's teachings and declared Fard Muhammad to be the latest Allah. Attracting growing attention in the late 1950s and 1960s, the NOI's influence expanded through high-profile members such as the black nationalist activist Malcolm X and the boxer Muhammad Ali. Deeming it a threat to domestic security, the Federal Bureau of Investigation worked to undermine the group. Following Elijah Muhammad's death in 1975, his son Warith Deen Mohammed took over the organization, moving it towards Sunni Islam and renaming it the World Community of Islam in the West. Members seeking to retain Elijah Muhammad's teachings re-established the Nation of Islam under Louis Farrakhan's leadership in 1977. Farrakhan has continued to develop the NOI's beliefs, for instance by drawing connections with Dianetics, and expanding its economic and agricultural operations.

Based in the United States, the Nation of Islam has also established a presence abroad, with membership open only to people of color. In 2007, it was estimated to have 50,000 members. The Nation has proven to be particularly successful at converting prisoners.