The cardinal virtues are four virtues of mind and character in both classical philosophy and Christian theology. They are prudence, justice, fortitude, and temperance. They form a virtue theory of ethics. The term cardinal comes from the Latin cardo (hinge); these four virtues are called “cardinal” because all other virtues fall under them and hinge upon them.

A virtue is a trait of excellence, including traits that may be moral, social, or intellectual. The cultivation and refinement of virtue is held to be the "good of humanity" and thus is valued as an end purpose of life or a foundational principle of being. In human practical ethics, a virtue is a disposition to choose actions that succeed in showing high moral standards: doing what is right and avoiding what is wrong in a given field of endeavour, even when doing so may be unnecessary from a utilitarian perspective. When someone takes pleasure in doing what is right, even when it is difficult or initially unpleasant, they can establish virtue as a habit. Such a person is said to be virtuous through having cultivated such a disposition. The opposite of virtue is vice, and the vicious person takes pleasure in habitual wrong-doing to their detriment.