Involuntary commitment, civil commitment, or involuntary hospitalization/hospitalisation, or informally in Britain sectioning, being sectioned, commitment, or being committed, is a legal process through which an individual who is deemed by a qualified person to have symptoms of severe mental disorder is detained in a psychiatric hospital (inpatient) where they can be treated involuntarily. This treatment may involve the administration of psychoactive drugs, including involuntary administration. In many jurisdictions, people diagnosed with mental health disorders can also be forced to undergo treatment while in the community; this is sometimes referred to as outpatient commitment and shares legal processes with commitment. Importantly, the term "involuntary commitment" in the United States does not always refer to a legal intervention, but rather refers to an ethical lens from the perspective of individual autonomy. Users of the term are therefore recommended to define precisely what they mean by "involuntary commitment," such as by clarifying the extent they refer to external pressure, civil rights, individual agency, competence and capacity, and ethics.

Criteria for civil commitment are established by laws which vary between nations. Commitment proceedings often follow a period of emergency hospitalization, during which an individual with acute psychiatric symptoms is confined for a relatively short duration (e.g. 72 hours) in a treatment facility for evaluation and stabilization by mental health professionals who may then determine whether further civil commitment is appropriate or necessary. Civil commitment procedures may take place in a court or only involve physicians. If commitment does not involve a court there is normally an appeal process that does involve the judiciary in some capacity, though potentially through a specialist court.

For most jurisdictions, involuntary commitment is applied to individuals believed to be experiencing a mental illness that impairs their ability to reason to such an extent that the agents of the law, state, or courts determine that decisions will be made for the individual under a legal framework. In some jurisdictions, this is a proceeding distinct from being found incompetent. Involuntary commitment is used in some degree for each of the following although different jurisdictions have different criteria. Some jurisdictions limit involuntary treatment to individuals who meet statutory criteria for presenting a danger to self or others. Other jurisdictions have broader criteria. The legal process by which commitment takes place varies between jurisdictions. Some jurisdictions have a formal court hearing where testimony and other evidence may also be submitted and the subject of the hearing is typically entitled to legal counsel and may challenge a commitment order through habeas corpus. Other jurisdictions have delegated these power to physicians, though may provide an appeal process that involves the judiciary but may also involve physicians. For example, in the UK a mental health tribunal consists of a judge, a medical member, and a lay representative.

Training is gradually becoming available in mental health first aid to equip community members such as teachers, school administrators, police officers, and medical workers with training in recognizing, and authority in managing, situations where involuntary evaluations of behavior are applicable under law. The extension of first aid training to cover mental health problems and crises is a quite recent development. A mental health first aid training course was developed in Australia in 2001 and has been found to improve assistance provided to persons with an alleged mental illness or mental health crisis. This form of training has now spread to a number of other countries (Canada, Finland, Hong Kong, Ireland, Singapore, Scotland, England, Wales, and the United States). Mental health triage may be used in an emergency room to make a determination about potential risk and apply treatment protocols.

Observation is sometimes used to determine whether a person warrants involuntary commitment. It is not always clear on a relatively brief examination whether a person should be committed.^{[citation needed]}

Austria, Belgium, Germany, Israel, the Netherlands, Northern Ireland, the Republic of Ireland, Russia, Taiwan, Ontario (Canada), and the United States have adopted commitment criteria based on the presumed danger of the defendant to self or to others.

People with suicidal thoughts may act on these impulses and harm or kill themselves.

People with psychosis are occasionally driven by their delusions or hallucinations to harm themselves or others. Research has found that those with schizophrenia are between 3.4 and 7.4 times more likely to engage in violent behaviour than members of the general public. However, because other confounding factors such as childhood adversity and poverty are correlated with both schizophrenia and violence it can be difficult to determine whether this effect is due to schizophrenia or other factors. In an attempt to avoid these confounding factors, researchers have tried comparing the rates of violence amongst people diagnosed with schizophrenia to their siblings in a similar manner to twin studies. In these studies people with schizophrenia are found to be between 1.3 and 1.8 times more likely to engage in violent behaviour.