Entryism (also referred to as entrism, occasionally as enterism) is a political strategy in which an organisation or state encourages its members or supporters to join another, usually larger organisation in an attempt to expand influence and expand their ideas and program. In situations where the organization being "entered" is hostile to entrism, the entrists may engage in a degree of subterfuge to hide the fact that they are an organisation in their own right. In some cases the alleged entryists perceive themselves as supporters of a newspaper and not members of an organization. While Marxists argue that entryism flows from the "demands of the class struggle", others allege it is more akin to infiltration.
Entryism does not involve dissolving the small organisation into the larger one. Entryism is often carried out in secrecy and often in organisations run on Leninist lines. The strategy of entryism is as old as politics itself.