The movement emerged in Jamaica among Jamaicans in the early 1930s, arising from an interpretation of Biblical prophecy partly based on Selassie's status as the only African monarch of a fully independent state, with the titles King of Kings and Conquering Lion of Judah (Revelation 5:5). Other characteristics of Rastafarianism include the spiritual use of cannabis, and various Afrocentric social and political aspirations, such as the teachings of Jamaican publicist, organizer, and black separatist Marcus Garvey (also often regarded as a prophet), whose political and cultural vision helped inspire a new world view.

The Rastafarian movement has spread throughout much of the world, largely through interest generated by reggae music—most notably, that of Jamaican singer/songwriter Bob Marley. By 2000, there were more than one million Rastafarians faithful worldwide. About five to ten percent of Jamaicans identify themselves as Rastafarian. Many Rastafarians follow an ital diet which essentially means living by the dietary Laws of Leviticus and Deuteronomy in the Old Testament.

Leonard Howell, who has been described as the "first Rasta," formed a commune which grew as large as 5,000 people at a place called Pinnacle, at St. Catherine in Jamaica.

Rastafarianism developed among an oppressed people who felt society had nothing to offer them except more suffering. Rastas may regard themselves as conforming to certain visions of how Africans should live, reclaiming what they see as a culture stolen from them when their ancestors were brought on slave ships to Jamaica, the movement's birthplace. The messages expounded by the Rastafarians promote love and respect for all living things and emphasize the paramount importance of human dignity and self-respect. Above all else, they speak of freedom from spiritual, psychological, as well as physical slavery and oppression. In their attempts to heal the wounds inflicted upon the African peoples by the imperialist nations of the world, Rastafarianism continually extol the virtue and superiority of African cultures and civilization past and present.

The doctrines of Rastafarianism depart radically from the norms of the conventional modern western mind, a trait of the movement deliberately encouraged by Rastas themselves. Unlike many religious groups that stress compliance with and recognition of the "powers-that-be," Rastafarianism instead stresses loyalty to their vision of "Zion," and rejection of modern society (called Babylon), which they see as thoroughly corrupt. "Babylon" in this case is considered to be rebelling against "Earth's Rightful Ruler" (JAH) ever since the days of king Nimrod.

This "way of life" is not merely to be assented to intellectually, or "belief" as the term is often used; it is used for the finding and knowledge of one's true identity. To follow and worship JAH Rastafari is to find, spread, and "trod" the unique path to which each individual Rasta was rightfully born. The movement is difficult to categorize, because Rastafarianism is not a centralized organization. Individual Rastafarians work out their religion for themselves, resulting in a wide variety of doctrines nevertheless also covered under the general umbrella of Rastafarianism.