In the sociological classifications of religious movements, a cult is a social group with socially deviant or novel beliefs and practices, although this is often unclear. Other researchers present a less-organized picture of cults on the basis that cults arise spontaneously around novel beliefs and practices. Groups said to be cults range in size from local groups with a few members to international organizations with millions.

Beginning in the 1930s, cults became the object of sociological study in the context of the study of religious behavior. From the 1940s the Christian countercult movement has opposed some sects and new religious movements, and it labelled them as cults for their “un-Christian” unorthodox beliefs. The secular anti-cult movement began in the 1970s and it opposed certain groups, often charging them with mind control and partly motivated in reaction to acts of violence committed by some of their members. Some of the claims and actions of the anti-cult movements have been disputed by scholars and by the news media, leading to further public controversy.