Individualism is the moral stance, political philosophy, ideology, and social outlook that emphasizes the worth or central role of the individual. Individualists promote realizing one's goals and desires, valuing independence and self-reliance, and advocating that the interests of the individual should gain precedence over the state or a social group, while opposing external interference upon one's own interests by society or institutions such as the government. Individualism makes the individual its focus, and so starts "with the fundamental premise that the human individual is of primary importance in the struggle for liberation".

Individualism represents one kind of sociocultural perspective and is often defined in contrast to other perspectives, such as communitarianism, collectivism and corporatism.

Individualism is also associated with artistic and bohemian interests and lifestyles, where there is a tendency towards self-creation and experimentation as opposed to tradition or popular mass opinions and behaviors, and it is associated with humanist philosophical positions and ethics. "Individualism" has also been used as a term denoting "[t]he quality of being an individual; individuality", related to possessing "[a]n individual characteristic; a quirk".

In the English language, the word individualism was first introduced as a pejorative by utopian socialists such as the Owenites in the late 1830s, although it is unclear if they were influenced by Saint-Simonianism or came up with it independently. A more positive use of the term in Britain came to be used with the writings of James Elishama Smith, a millenarian-turned-socialist and Christian Israelite. Although an early follower of Robert Owen, he eventually rejected Owen's collective idea of property and found in individualism a "universalism" that allowed for the development of the "original genius". Without individualism, Smith argued that individuals cannot amass property to increase one's happiness. William Maccall, another Unitarian preacher and probably an acquaintance of Smith, came somewhat later, although influenced by John Stuart Mill, Thomas Carlyle and German Romanticism, to the same positive conclusions in his 1847 work Elements of Individualism.

An individual is a person or any specific object in a collection. In the 15th century and earlier, and also today within the fields of statistics and metaphysics, individual means "indivisible", typically describing any numerically singular thing, but sometimes meaning "a person" as in "the problem of proper names". From the 17th century on, individual indicates separateness, as in individualism. Individuality is the state or quality of being an individuated being; a person separated from everything with unique character by possessing their own needs, goals, and desires in comparison to other people.

The principle of individuation, or principium individuationis, describes the manner in which a thing is identified as distinguished from other things. For Carl Jung, individuation is a process of transformation, whereby the personal and collective unconscious is brought into consciousness (by means of dreams, active imagination or free association to take examples) to be assimilated into the whole personality. It is a completely natural process necessary for the integration of the psyche to take place. Jung considered individuation to be the central process of human development. In L'individuation psychique et collective, Gilbert Simondon developed a theory of individual and collective individuation in which the individual subject is considered as an effect of individuation rather than a cause. Thus, the individual atom is replaced by a never-ending ontological process of individuation. Individuation is an always incomplete process, always leaving a "pre-individual" left-over, itself making possible future individuations. The philosophy of Bernard Stiegler draws upon and modifies the work of Gilbert Simondon on individuation and also upon similar ideas in Friedrich Nietzsche and Sigmund Freud. For Stiegler, "the I, as a psychic individual, can only be thought in relationship to we, which is a collective individual. The I is constituted in adopting a collective tradition, which it inherits and in which a plurality of I's acknowledge each other's existence."

Individualism holds that a person taking part in society attempts to learn and discover what their own interests are on a personal basis, without a presumed following of the interests of a societal structure (an individualist need not be an egoist). The individualist does not necessarily follow one particular philosophy. They may create an amalgamation of elements of many philosophies, based on personal interests in particular aspects that they find of use. On a societal level, the individualist participates on a personally structured political and moral ground. Independent thinking and opinion is a necessary trait of an individualist. Jean-Jacques Rousseau, claims that his concept of general will in The Social Contract is not the simple collection of individual wills and that it furthers the interests of the individual (the constraint of law itself would be beneficial for the individual, as the lack of respect for the law necessarily entails, in Rousseau's eyes, a form of ignorance and submission to one's passions instead of the preferred autonomy of reason).

Individualism versus collectivism is a common dichotomy in cross-cultural research. Global comparative studies have found that the world's cultures vary in the degree to which they emphasize individual autonomy, freedom and initiative (individualistic traits), respectively conformity to group norms, maintaining traditions and obedience to in-group authority (collectivistic traits). Cultural differences between individualism and collectivism are differences in degrees, not in kind. Cultural individualism is strongly correlated with GDP per capita and venture capital investments. The cultures of economically developed regions such as Australia, New Zealand, Japan, South Korea, North America and Western Europe are the most individualistic in the world. Middle income regions such as Eastern Europe, South America and mainland East Asia have cultures which are neither very individualistic nor very collectivistic. The most collectivistic cultures in the world are from economically developing regions such as the Middle East and Northern Africa, Sub-Saharan Africa, South and South-East Asia, Central Asia and Central America. Against this background, a number of prominent authors from various disciplines (e.g., Louis Dumont, Geert Hofstede, Anthony Giddens, Zygmunt Bauman, Ronald Inglehart) have supported the influential thesis that the modernization of a society goes hand in hand with an increasing degree of individualization. However, this thesis has also found its critics, who point out, among other things, that the cultural-historical development of individualism from antiquity to the present has not proceeded in a straight line, that some societies with a more collectivist orientation are nevertheless highly modernized and that the concepts of individualism, collectivism and modernity lack conceptual clarity so that an appropriately differentiated analysis of the alleged connection is still lacking.