Illegalism is a tendency of anarchism that developed primarily in France, Italy, Belgium and Switzerland during the late 1890s and early 1900s as an outgrowth of individualist anarchism. Illegalists embrace criminality either openly or secretly as a lifestyle. Illegalism does not specify the type of crime, though it is associated with theft and shoplifting.

Anarchism is a political philosophy and movement that is against all forms of authority and seeks to abolish the institutions it claims maintain unnecessary coercion and hierarchy, typically including the state and capitalism. Anarchism advocates for the replacement of the state with stateless societies and voluntary free associations. As a historically left-wing movement, this reading of anarchism is placed on the farthest left of the political spectrum, usually described as the libertarian wing of the socialist movement.