An epiphany (from the ancient Greek ἐπιφάνεια, epiphanea, "manifestation, striking appearance") is an experience of a sudden and striking realization. Generally the term is used to describe a scientific breakthrough or a religious or philosophical discovery, but it can apply in any situation in which an enlightening realization allows a problem or situation to be understood from a new and deeper perspective. Epiphanies are studied by psychologists and other scholars, particularly those attempting to study the process of innovation.

Epiphanies are relatively rare occurrences and generally follow a process of significant thought about a problem. Often they are triggered by a new and key piece of information, but importantly, a depth of prior knowledge is required to allow the leap of understanding. Famous epiphanies include Archimedes's discovery of a method to determine the volume of an irregular object ("Eureka!") and Isaac Newton's realization that a falling apple and the orbiting moon are both pulled by the same force.