Foreign internal defense is a term used by the militaries of some countries, including the United States, France, and the United Kingdom, to describe an integrated and synchronized, multi-disciplinary (and often joint, interagency, and international as well) approach to combating actual or threatened insurgency in a foreign state. This foreign state is known as the Host Nation (HN).

Foreign internal defense (FID) is an approach to counter insurgency operations. It involves military deployment of counter-insurgency specialists. The doctrine calls for a close working relationship between the host nation government and security forces with outside diplomatic, information, intelligence, military, economic, and other specialists. Operations are typically conducted by military forces deployed in conjunction with host nations; however, these operations can be supplemented by supporting clandestine and clandestine operations of special forces as well as direct action carried out by paramilitary forces.