A civilization (also spelled civilisation in British English) is any complex society characterized by the development of the state, social stratification, urbanization, and symbolic systems of communication beyond signed or spoken languages (namely, writing systems).

Civilizations are organized around densely populated settlements, divided into more or less rigid hierarchical social classes of division of labour, often with a ruling elite and subordinate urban and rural populations, which engage in intensive agriculture, mining, small-scale manufacture and trade. Civilization concentrates power, extending human control over the rest of nature, including over other human beings. Civilizations are characterized by elaborate agriculture, architecture, infrastructure, technological advancement, currency, taxation, regulation, and specialization of labour.

Historically, a civilization has often been understood as a larger and "more advanced" culture, in implied contrast to smaller, supposedly less advanced cultures, even societies within civilizations themselves and within their histories. Generally civilization contrasts with non-centralized tribal societies, including the cultures of nomadic pastoralists, Neolithic societies, or hunter-gatherers.

The word civilization relates to the Latin civitas or 'city'. As the National Geographic Society has explained it: "This is why the most basic definition of the word civilization is 'a society made up of cities.'" The earliest emergence of civilizations is generally connected with the final stages of the Neolithic Revolution in West Asia, culminating in the relatively rapid process of urban revolution and state formation, a political development associated with the appearance of a governing elite.

The English word civilization comes from the French civilisé ('civilized'), from Latin: civilis ('civil'), related to civis ('citizen') and civitas ('city'). The fundamental treatise is Norbert Elias's The Civilizing Process (1939), which traces social mores from medieval courtly society to the early modern period. In The Philosophy of Civilization (1923), Albert Schweitzer outlines two opinions: one purely material and the other material and ethical. He said that the world crisis was from humanity losing the ethical idea of civilization, "the sum total of all progress made by man in every sphere of action and from every point of view in so far as the progress helps towards the spiritual perfecting of individuals as the progress of all progress".

Related words like "civility" developed in the mid-16th century. The abstract noun "civilization", meaning "civilized condition", came in the 1760s, again from French. The first known use in French is in 1757, by Victor de Riqueti, marquis de Mirabeau, and the first use in English is attributed to Adam Ferguson, who in his 1767 Essay on the History of Civil Society wrote, "Not only the individual advances from infancy to manhood but the species itself from rudeness to civilisation". The word was therefore opposed to barbarism or rudeness, in the active pursuit of progress characteristic of the Age of Enlightenment.

In the late 1700s and early 1800s, during the French Revolution, "civilization" was used in the singular, never in the plural, and meant the progress of humanity as a whole. This is still the case in French. The use of "civilizations" as a countable noun was in occasional use in the 19th century, but has become much more common in the later 20th century, sometimes just meaning culture (itself in origin an uncountable noun, made countable in the context of ethnography). Only in this generalized sense does it become possible to speak of a "medieval civilization", which in Elias's sense would have been an oxymoron. Using the terms "civilization" and "culture" as equivalents is controversial and generally rejected, so that, for example, some types of culture are not normally described as civilizations.

Already in the 18th century, civilization was not always seen as an improvement. One historically important distinction between culture and civilization is from the writings of Rousseau, particularly his work about education, Emile. Here, civilization, being more rational and socially driven, is not fully in accord with human nature, and "human wholeness is achievable only through the recovery of or approximation to an original discursive or pre-rational natural unity" (see noble savage). From this, a new approach was developed, especially in Germany, first by Johann Gottfried Herder and later by philosophers such as Kierkegaard and Nietzsche. This sees cultures as natural organisms, not defined by "conscious, rational, deliberative acts", but a kind of pre-rational "folk spirit". Civilization, in contrast, though more rational and more successful in material progress, is unnatural and leads to "vices of social life" such as guile, hypocrisy, envy and avarice. In World War II, Leo Strauss, having fled Germany, argued in New York that this opinion of civilization was behind Nazism and German militarism and nihilism.