Modernity, a topic in the humanities and social sciences, is both a historical period (the modern era) and the ensemble of particular socio-cultural norms, attitudes and practices that arose in the wake of the Renaissance—in the Age of Reason of 17th-century thought and the 18th-century Enlightenment. Commentators variously consider the era of modernity to have ended by 1930, with World War II in 1945, or as late as the period falling between the 1980s and 1990s; the following era is often referred to as "postmodernity". The term "contemporary history" is also used to refer to the post-1945 timeframe, without assigning it to either the modern or postmodern era. (Thus "modern" may be used as a name of a particular era in the past, as opposed to meaning "the current era".)

Depending on the field, modernity may refer to different time periods or qualities. In historiography, the 16th to 18th centuries are usually described as early modern, while the long 19th century corresponds to modern history proper. While it includes a wide range of interrelated historical processes and cultural phenomena (from fashion to modern warfare), it can also refer to the subjective or existential experience of the conditions they produce, and their ongoing impact on human culture, institutions, and politics.

As an analytical concept and normative idea, modernity is closely linked to the ethos of philosophical and aesthetic modernism; political and intellectual currents that intersect with the Enlightenment; and subsequent developments such as existentialism, modern art, the formal establishment of social science, and contemporaneous antithetical developments such as Marxism. It also encompasses the social relations associated with the rise of capitalism, and shifts in attitudes associated with secularization, liberalization, modernization and post-industrial life.

By the late 19th and early 20th centuries, modernist art, politics, science and culture had come to dominate not only Western Europe and North America, but almost every populated area on the globe, including movements opposing the West or opposing globalization. The modern era is closely associated with the development of individualism, capitalism, urbanization and progressivism—that is, the belief in the possibilities of technological and political progress. Perceptions of problems arising from modernization, which can include the advent of world wars, the reduced role of religion in some societies, or the erosion of traditional cultural norms, have also led to anti-modernization movements. Optimism and the belief in consistent progress (also referred to as whig history) have been subject to criticism in postmodern thought, while the global hegemonic dominance (particularly in the form of imperialism and colonialism) of various powers in western Europe and Anglo-America for most of the period has been criticized in postcolonial theory.

In the context of art history, modernity (Fr. modernité) has a more limited sense, modern art covering the period of c. 1860–1970. Use of the term in this sense is attributed to Charles Baudelaire, who in his 1863 essay "The Painter of Modern Life", designated the "fleeting, ephemeral experience of life in an urban metropolis", and the responsibility art has to capture that experience. In this sense, the term refers to "a particular relationship to time, one characterized by intense historical discontinuity or rupture, openness to the novelty of the future, and a heightened sensitivity to what is unique about the present".^{[failed verification]}

The Late Latin adjective modernus, a derivation from the adverb modo ("presently, just now", also "method"), is attested from the 5th century CE, at first in the context of distinguishing the Christian era of the Later Roman Empire from the Pagan era of the Greco-Roman world. In the 6th century CE, Roman historian and statesman Cassiodorus appears to have been the first writer to use modernus ("modern") regularly to refer to his own age.

The terms antiquus and modernus were used in a chronological sense in the Carolingian era. For example, a magister modernus referred to a contemporary scholar, as opposed to old authorities such as Benedict of Nursia. In its early medieval usage, the term modernus referred to authorities regarded in medieval Europe as younger than the Greco-Roman scholars of Classical antiquity and/or the Church Fathers of the Christian era, but not necessarily to the present day, and could include authors several centuries old, from about the time of Bede, i.e. referring to the time after the foundation of the Order of Saint Benedict and/or the fall of the Western Roman Empire.

The Latin adjective was adopted in Middle French, as moderne, by the 15th century, and hence, in the early Tudor period, into Early Modern English. The early modern word meant "now existing", or "about the present times", not necessarily with a positive connotation. English author and playwright William Shakespeare used the term modern in the sense of "everyday, ordinary, commonplace".