Informed consent is a process for getting permission before conducting a healthcare intervention on a person, for conducting some form of research on a person, or for disclosing a person's information. A health care provider may ask a patient to consent to receive therapy before providing it, a clinical researcher may ask a research participant before enrolling that person into a clinical trial, and a researcher may ask a research participant before starting some form of controlled experiment. Informed consent is collected according to guidelines from the fields of medical ethics and research ethics.

Free consent is a cognate term enshrined in the International Covenant on Civil and Political Rights. The Covenant was adopted in 1966 by the United Nations, and supposed to be in force by 23 March 1976. Article seven prohibits experiments conducted without the "free consent to medical or scientific experimentation" of the subject. As of September 2019, the Covenant has 173 parties and six more signatories without ratification.

An informed consent can be said to have been given based upon a clear appreciation and understanding of the facts, implications, and consequences of an action. To give informed consent, the individual concerned must have adequate reasoning faculties and be in possession of all relevant facts. Impairments to reasoning and judgment that may prevent informed consent include basic intellectual or emotional immaturity, high levels of stress such as posttraumatic stress disorder (PTSD) or a severe intellectual disability, severe mental disorder, intoxication, severe sleep deprivation, Alzheimer's disease, or being in a coma.

Obtaining informed consent is not always required. If an individual is considered unable to give informed consent, another person is generally authorized to give consent on his behalf, e.g., parents or legal guardians of a child (though in this circumstance the child may be required to provide informed assent) and conservators for the mentally disordered, or consent can be assumed through the doctrine of implied consent, e.g., when an unconscious person will die without immediate medical treatment.

In cases where an individual is provided insufficient information to form a reasoned decision, serious ethical issues arise. Such cases in a clinical trial in medical research are anticipated and prevented by an ethics committee or Institutional Review Board.

Informed Consent Form (ICF) templates can be found on the website of the World Health Organization.