Xenophobia is the fear and distrust of that which is perceived to be foreign or strange. Xenophobia can manifest itself in many ways involving the relations and perceptions of an ingroup towards an outgroup, including a fear of losing identity, suspicion of its activities, aggression, and desire to eliminate its presence to secure a presumed purity. Xenophobia is a political term and not a recognized medical phobia.

Xenophobia can also be exhibited in the form of an "uncritical exaltation of another culture" in which a culture is ascribed "an unreal, stereotyped and exotic quality". The terms xenophobia and racism are sometimes confused and used interchangeably because people who share a national origin may also belong to the same race. Due to this, xenophobia is usually distinguished by opposition to foreign culture.

Dictionary definitions of "xenophobia" include: "deep-rooted fear towards foreigners" (Oxford English Dictionary; OED), and "fear of the unfamiliar" (Webster's). The word comes from the Ancient Greek words ξένος ("xenos"), meaning "strange", "foreigner", and φόβος ("phobos"), meaning "fear".

A scholarly definition of xenophobia, according to Andreas Wimmer, is "an element of a political struggle about who has the right to be cared for by the state and society: a fight for the collective goods of the modern state". In other words, xenophobia arises when people feel that their rights to benefit from the government is being subverted by other people's rights.