Egoism is a philosophy concerned with the role of the self, or ego, as the motivation and goal of one's own action. Different theories of egoism encompass a range of disparate ideas and can generally be categorized into descriptive or normative forms. That is, they may be interested in either describing that people do act in self-interest or prescribing that they should. Other definitions of egoism may instead emphasise action according to one's will rather than one's self-interest, and furthermore posit that this is a truer sense of egoism.

The New Catholic Encyclopedia states of egoism that it "incorporates in itself certain basic truths: it is natural for man to love himself; he should moreover do so, since each one is ultimately responsible for himself; pleasure, the development of one's potentialities, and the acquisition of power are normally desirable." The moral censure of self-interest is a common subject of critique in egoist philosophy, with such judgments being examined as means of control and the result of power relations. Egoism may also reject that insight into one's internal motivation can arrive extrinsically, such as from psychology or sociology, though, for example, this is not present in the philosophy of Friedrich Nietzsche.