Rastafari refer to their beliefs, which are based on a specific interpretation of the Bible, as "Rastalogy". Central is a monotheistic belief in a single God—referred to as Jah—who partially resides within each individual. The former emperor of Ethiopia, Haile Selassie, is given central importance. Many Rastas regard him as an incarnation of Jah on Earth and as the Second Coming of Christ. Others regard him as a human prophet who fully recognised the inner divinity within every individual. Rastafari is Afrocentric and focuses its attention on the African diaspora, which it believes is oppressed within Western society, or "Babylon". Many Rastas call for the resettlement of the African diaspora in either Ethiopia or Africa more widely, referring to this continent as the Promised Land of "Zion". Other interpretations shift focus on to the adoption of an Afrocentric attitude while living outside of Africa. Rastas refer to their practices as "livity". Communal meetings are known as "groundations", and are typified by music, chanting, discussions, and the smoking of cannabis, the latter being regarded as a sacrament with beneficial properties. Rastas place emphasis on what they regard as living 'naturally', adhering to ital dietary requirements, allowing their hair to form into dreadlocks, and following patriarchal gender roles.
Rastafari originated among impoverished and socially disenfranchised Afro-Jamaican communities in 1930s Jamaica. Its Afrocentric ideology was largely a reaction against Jamaica's then-dominant British colonial culture. It was influenced by both Ethiopianism and the Back-to-Africa movement promoted by black nationalist figures like Marcus Garvey. The movement developed after several Christian clergymen, most notably Leonard Howell, proclaimed that the crowning of Haile Selassie as Emperor of Ethiopia in 1930 fulfilled a Biblical prophecy. By the 1950s, Rastafari's counter-cultural stance had brought the movement into conflict with wider Jamaican society, including violent clashes with law enforcement. In the 1960s and 1970s it gained increased respectability within Jamaica and greater visibility abroad through the popularity of Rasta-inspired reggae musicians like Bob Marley. Enthusiasm for Rastafari declined in the 1980s, following the deaths of Haile Selassie and Marley.
The Rasta movement is organised on a largely cellular basis. There are several denominations, or "Mansions of Rastafari", the most prominent of which are the Nyahbinghi, Bobo Ashanti, and the Twelve Tribes of Israel, each of which offers different interpretations of Rasta belief. There are an estimated 700,000 to 1 million Rastas across the world; the largest population is in Jamaica although communities can be found in most of the world's major population centres. The majority of practitioners are of black African descent, although a minority come from other racial groups.
Scholars of religion have categorised Rastafari as a new religious movement, a new social movement, or as a social movement. The scholar of religion Leonard E. Barrett referred to it as a sect, and the sociologist Ernest Cashmore as a cult, while scholar of religion Ennis B. Edmonds argued that it could best be understood as a revitalization movement. Although Rastafari focuses on Africa as a source of identity, the scholar of religion Maboula Soumahoro noted that it was not an "authentic" African religion but an example of creolization, a product of the unique social environment that existed in the Americas. Edmonds also suggested that Rastafari was "emerging" as a world religion, not because of the number of adherents that it had, but because of its global spread. Many Rastas themselves, however, do not regard it as a religion, instead referring to it as a "way of life". In 1989, a British Industrial Tribunal concluded that—for the purposes of the Race Relations Act 1976—Rastafarians could be considered an ethnic group because they have a long, shared heritage which distinguished themselves from other groups, their own cultural traditions, a common language, and a common religion.
The term "Rastafari" derives from the pre-regnal title of Haile Selassie; the term "Ras" means a duke or prince, while "Tafari Makonen" was his name. It is unknown why the early Rastas adopted this form of Haile Selassie's name as the basis of their religion's name. Many commentators—including some academic sources—refer to the movement as "Rastafarianism". This term has also been used by some practitioners. However, "Rastafarianism" is considered offensive by most Rastafari, who, being critical of "isms" or "ians" (which they see as a typical part of "Babylon" culture), dislike being labelled as an "ism" or "ian" themselves. Cashmore urged fellow academics not to use this term, which he described as "insensitive".