Ethnocentrism in social science and anthropology—as well as in colloquial English discourse—means to apply one's own culture or ethnicity as a frame of reference to judge other cultures, practices, behaviors, beliefs, and people, instead of using the standards of the particular culture involved. Since this judgment is often negative, some people also use the term to refer to the belief that one's culture is superior to, or more correct or normal than, all others—especially regarding the distinctions that define each ethnicity's cultural identity, such as language, behavior, customs, and religion. In common usage, it can also simply mean any culturally biased judgment. For example, ethnocentrism can be seen in the common portrayals of the Global South and the Global North.

Ethnocentrism is sometimes related to racism, stereotyping, discrimination, or xenophobia. However, the term "ethnocentrism" does not necessarily involve a negative view of the others' race or indicate a negative connotation. The opposite of ethnocentrism is cultural relativism, a guiding philosophy stating the best way to understand a different culture is through their perspective rather than judging them from the subjective viewpoints shaped by one's own cultural standards.

The term "ethnocentrism" was first applied in the social sciences by American sociologist William G. Sumner. In his 1906 book, Folkways, Sumner describes ethnocentrism as "the technical name for the view of things in which one's own group is the center of everything, and all others are scaled and rated with reference to it." He further characterized ethnocentrism as often leading to pride, vanity, the belief in one's own group's superiority, and contempt for outsiders.

Over time, ethnocentrism developed alongside the progression of social understandings by people such as social theorist Theodore W. Adorno. In Adorno's The Authoritarian Personality, he and his colleagues of the Frankfurt School established a broader definition of the term as a result of "in group-out group differentiation", stating that ethnocentrism "combines a positive attitude toward one's own ethnic/cultural group (the in-group) with a negative attitude toward the other ethnic/cultural group (the out-group)." Both of these juxtaposing attitudes are also a result of a process known as social identification and social counter-identification.