In philosophy, potentiality and actuality are a pair of closely connected principles which Aristotle used to analyze motion, causality, ethics, and physiology in his Physics, Metaphysics, Nicomachean Ethics, and De Anima.

The concept of potentiality, in this context, generally refers to any "possibility" that a thing can be said to have. Aristotle did not consider all possibilities the same, and emphasized the importance of those that become real of their own accord when conditions are right and nothing stops them. Actuality, in contrast to potentiality, is the motion, change or activity that represents an exercise or fulfillment of a possibility, when a possibility becomes real in the fullest sense.

These concepts, in modified forms, remained very important into the Middle Ages, influencing the development of medieval theology in several ways. In modern times the dichotomy has gradually lost importance, as understandings of nature and deity have changed. However the terminology has also been adapted to new uses, as is most obvious in words like energy and dynamic. These were words first used in modern physics by the German scientist and philosopher, Gottfried Wilhelm Leibniz. Aristotle's concept of entelechy retains influence on recent concepts of biological "entelechy".