In common law legal systems, laches ( "latches", ; Law French: remissness, dilatoriness, from Old French laschesse) is a lack of diligence and activity in making a legal claim, or moving forward with legal enforcement of a right, particularly in regard to equity. This means that it is an unreasonable delay that can be viewed as prejudicing the opposing party. When asserted in litigation, it is an equity defense, that is, a defense to a claim for an equitable remedy.

The person invoking laches is asserting that an opposing party has "slept on its rights", and that, as a result of this delay, circumstances have changed, witnesses or evidence may have been lost or no longer available, etc., such that it is no longer a just resolution to grant the plaintiff's claim. Laches is associated with the maxim of equity, "Equity aids the vigilant", not those who sleep on their rights. Put another way, failure to assert one's rights in a timely manner can result in a claim being barred by laches.