Duress (coercion) (as a term of jurisprudence) is a possible defense, via excuse, by which a defendant may argue that they should not be held criminally liable for actions which broke the law. Black's Law Dictionary (6th ed.) defines duress as: "any unlawful threat or coercion used...to induce another to act [or not act] in a manner [they] otherwise would not [or would]." A possible example of duress would involve robbing a bank in order to pay a ransom. Courts generally do not accept a defense of duress when harm done by the defendant, such as murder, was greater than the court's perception of the coercive influence.

A contract entered under duress is voidable. The concept of duress has to be distinguished from undue influence .