The expression military–industrial complex (MIC) describes the relationship between a country's military and the defense industry that supplies it, seen together as a vested interest which influences public policy. A driving factor behind the relationship between the military and the defense-minded corporations is that both sides benefit—one side from obtaining weapons, and the other from being paid to supply them. The term is most often used in reference to the system behind the armed forces of the United States, where the relationship is most prevalent due to close links among defense contractors, the Pentagon, and politicians. The expression gained popularity after a warning of the relationship's detrimental effects, in the farewell address of U.S. President Dwight D. Eisenhower on January 17, 1961.

The arms industry, also known as the defence industry, military industry, or the arms trade, is a global industry which manufactures and sells weapons and military technology. Public sector and private sector firms conduct research and development, engineering, production, and servicing of military material, equipment, and facilities. Customers are the armed forces of states, and civilians. An arsenal is a place where arms and ammunition – whether privately or publicly owned – are made, maintained and repaired, stored, or issued, in any combination. Products of the arms industry include weapons, munitions, weapons platforms, military communications and other electronics, and more. The arms industry also provides other logistical and operational support.