In sociology and in political science, the term The Establishment describes the dominant social group, the élite who control a polity, an organization, or an institution. In the praxis of power, The Establishment usually is a self-selecting, closed élite entrenched within specific institutions — hence, a relatively small social class can exercise all socio-political control.

In 1955, the journalist Henry Fairlie popularized the contemporary usage of the term The Establishment to denote the network of socially prominent and politically important people:

By the ‘Establishment’ I do not mean only the centres of official power — though they are certainly part of it — but rather the whole matrix of official and social relations within which power is exercised. The exercise of power in Britain (more specifically, in England) cannot be understood unless it is recognised that it is exercised socially.

Consequently, the term the Establishment became common usage in the press of London; The Oxford English Dictionary cites Fairlie's column originating the British usages of the term the Establishment, as in the established church denoting the official Church of England. Moreover, in sociologic jargon, an outsider is the person who is not a member of The Establishment.