Coercion () involves compelling a party to act in an involuntary manner by the use of threats, including threats to use force against that party. It involves a set of forceful actions which violate the free will of an individual in order to induce a desired response. These actions may include extortion, blackmail, or even torture and sexual assault. For example, a bully may demand lunch money from a student where refusal results in the student getting beaten.

Common-law systems codify the act of violating a law while under coercion as a duress crime.

Coercion used as leverage may force victims to act in a way contrary to their own interests. Coercion can involve not only the infliction of bodily harm, but also psychological abuse (the latter intended to enhance the perceived credibility of the threat). The threat of further harm may also lead to the acquiescence of the person being coerced.

The concepts of coercion and persuasion are similar, but various factors distinguish the two. These include the intent, the willingness to cause harm, the result of the interaction, and the options available to the coerced party.^: 126

John Rawls, Thomas Nagel, Ronald Dworkin, and other political authors argue that the state is coercive.^: 28 In 1919 Max Weber (1864-1920), building on the view of Ihering (1818-1892), defined a state as "a human community that (successfully) claims a monopoly on the legitimate use of physical force". Morris argues that the state can operate through incentives rather than coercion.^: 42 Healthcare systems may use informal coercion to make a patient adhere to a doctor's treatment plan. Under certain circumstances, medical staff may use physical coercion to treat a patient involuntarily.