A ritual is a sequence of activities involving gestures, words, actions, or objects, performed according to a set sequence. Rituals may be prescribed by the traditions of a community, including a religious community. Rituals are characterized, but not defined, by formalism, traditionalism, invariance, rule-governance, sacral symbolism, and performance.

Rituals are a feature of all known human societies. They include not only the worship rites and sacraments of organized religions and cults, but also rites of passage, atonement and purification rites, oaths of allegiance, dedication ceremonies, coronations and presidential inaugurations, marriages, funerals and more. Even common actions like hand-shaking and saying "hello" may be termed as rituals.

The field of ritual studies has seen a number of conflicting definitions of the term. One given by Kyriakidis is that a ritual is an outsider's or "etic" category for a set activity (or set of actions) that, to the outsider, seems irrational, non-contiguous, or illogical. The term can be used also by the insider or "emic" performer as an acknowledgement that this activity can be seen as such by the uninitiated onlooker.

In psychology, the term ritual is sometimes used in a technical sense for a repetitive behavior systematically used by a person to neutralize or prevent anxiety; it can be a symptom of obsessive–compulsive disorder but obsessive-compulsive ritualistic behaviors are generally isolated activities.