An egoist is a person who is preoccupied with their own interests and has an inflated opinion of their personal features and importance. They have a strong tendency to talk about themselves in a self-promoting fashion and may be arrogant and boastful with a grandiose sense of their own importance. Egotism is closely related to an egocentric love for ones imagined self or narcissism. Egoism, on the other hand, is the constant pursuit of ones self-interest. Various forms of "empirical egoism" have been considered consistent with egotism, but do not necessarily require having an inflated sense of self.

In philosophy, egoism can be a descriptive or a normative position. Psychological egoism, the most famous descriptive position, claims that each person has but one ultimate aim: their own welfare. Normative forms of egoism make claims about what one ought to do, rather than describe what one does do. Ethical egoism claims that one morally ought to perform some action if and only if, and because, performing that action maximizes their self-interest. Rational egoism claims that one ought to perform some action if and only if, and because, performing that action maximizes their self-interest.