A legal condition wherein a person is in a state to clearly understand the facts and consequences of an action, and agrees to it after reviewing these facts and consequences. Factors such as severe mental illness or retardation, intoxication, or coma can render people unable to give their informed consent.

Example: A researcher running a clinical trial for a new medication presents each subject with a document outlining any potential risks inherent in the study; people who wish to participate must indicate their consent by signing it.