The Department of National Defence is the department of the Government of Canada which supports the Canadian Armed Forces in its role of defending Canadian national interests domestically and internationally. The department is a civilian organization, part of the public service, and supports the armed forces; however, as a civilian organization is separate and not part of the military itself. National Defence is the largest department of the Government of Canada in terms of budget, and it is the department with the largest number of buildings.

The Canadian Armed Forces are the unified military forces of Canada, including land, sea, and air commands referred to as the Canadian Army, Royal Canadian Navy, and the Royal Canadian Air Force. The CAF also operates several other commands, including the Canadian Forces Intelligence Command, the Canadian Joint Operations Command, and the Canadian Special Operations Forces Command. Personnel may belong to either the Regular Force or the Reserve Force, which has four sub-components: the Primary Reserve, Supplementary Reserve, Cadet Organizations Administration and Training Service, and the Canadian Rangers. Under the National Defence Act, the Canadian Armed Forces are an entity separate and distinct from the Department of National Defence, which also exists as the civilian support system for the forces.