Hazing (American English), initiation, beasting (British English), bastardisation (Australian English), ragging (South Asian English) or deposition refers to any activity expected of someone in joining or participating in a group that humiliates, degrades, abuses, or endangers them regardless of a person's willingness to participate.

Hazing is seen in many different types of social groups, including gangs, sports teams, schools, cliques, universities, fire departments, law enforcement, military units, prisons, fraternities and sororities, and even workplaces in some cases. The initiation rites can range from relatively benign pranks to protracted patterns of behavior that rise to the level of abuse or criminal misconduct.

Hazing is often prohibited by law or institutions such as colleges and universities because it may include either physical or psychological abuse, such as humiliation, nudity, or sexual abuse. Hazing activities have sometimes caused injuries or deaths.

While one explanation for hazing is that it increases group cohesion or solidarity, laboratory and observational evidence on its impacts on solidarity are inconclusive. Other explanations include displaying dominance, eliminating less committed members, and protecting groups that provide large automatic benefits for membership from exploitation by new members.

In some languages, terms with a religious theme or etymology are preferred, such as baptism or purgatory (e.g. baptême in Belgian French, doop in Belgian Dutch, chrzest in Polish) or variations on a theme of naïveté and the rite of passage such as a derivation from a term for freshman, for example bizutage in European French, ontgroening ('de-green[horn]ing') in Dutch and Afrikaans (South Africa and Namibia), novatada in Spanish, from novato, meaning newcomer or rookie or a combination of both, such as in the Finnish mopokaste (literally 'moped baptism'). In Latvian, the word iesvētības, which means 'in-blessings', is used, also standing for religious rites of passage, especially confirmation. In Swedish, the term used is nollning, literally 'zeroing', as the first-year hazees still are 'zeroes' before attending their first year. In Portugal, the term praxe, which means 'practice' or 'habit', is used for initiation. At education establishments in India, Pakistan, Bangladesh, and Sri Lanka, this practice involves existing students baiting new students and is called ragging.

Hazings are sometimes concentrated in a single session, which may be called a hell night, prolonged to a hell week, or over a long period, resembling fagging. In the Italian military, the term used was nonnismo, from nonno (literally 'grandfather'), a jargon term used for the soldiers who had already served for most of their draft period. A similar equivalent term exists in the Russian military, where a hazing phenomenon known as dedovshchina (дедовщи́на) exists, meaning roughly 'grandfather' or the slang term 'gramps' (referring to the senior corps of soldiers in their final year of conscription).

One way of initiating a new member into a street gang is for multiple other members of the gang to assault the new member with a beating.

Hazing activities can involve ridicule and humiliation within the group or in public, while other hazing incidents are akin to pranks. A snipe hunt is such a prank when a newcomer or credulous person is given an impossible task. Examples of snipe hunts include being sent to find a tin of Tartan paint or a "dough repair kit" in a bakery. While in the early 1900s, rookies in the Canadian military were ordered to obtain a "brass magnet" when brass is not magnetic.