The Ministry of National Defense (Spanish: Ministerio de Defensa Nacional) is the cabinet-level administrative office in charge of "maintaining the independence and sovereignty" of Chile. It is also charged with planning, directing, coordinating, executing, controlling and informing the defense policies formulated by the President of Chile. The minister supervises all the Chilean armed forces. It is Chile's ministry of defence.

During the first days of the independence movements, the senior "secretary" of the respective Junta would function as the Secretary of Government with administrative power over the army. The office officially first came to be on 17 March 1814, when then Supreme Director Francisco de la Lastra dictated the Constitutional Norms approved on that date. It was then named Secretariat of War. It was abolished the same year by the Spanish authorities when, after the Battle of Rancagua, they re-asserted royal power.

On 23 October 1818, after independence the secretariat was re-established, but this time with the inclusion of the Department of Navy as a "Secretariat of War and Navy" (1818–1837), though in common usage, the secretaries started to be called ministers when they held both secretariats (War and Navy) concurrently. Later on 1 February 1837 the office was officially renamed "Ministry of War and Navy" (1837–1932). In 1924, War and Navy were separated into two independent ministries, but on 8 July 1932 both branches were reunited again into one ministry renamed "Ministry of Defense", with the addition of the department of Aviation that had belonged to the Ministry of the Interior until that date.

On 28 October 1947, by Decree 2.320, it fell under the purview of this ministry the control of the Supreme Command of National Defense, the General Staff of the Armed Forces, the Central Purchasing Committee of the Armed Forces, the Civil Defense Forces and the Chilean chapter of the Red Cross. In 1960, the oversight was expanded to include the Superior Council on National Security (Consusena) and the Council of Commanders-in-Chief. According to Decree 200 of 15 April 1976, the oversight was again expanded to include the National Police (Carabineros and Investigaciones).

As indicated before, this ministry has undergone several reorganizations during its long history, reflected in its different names:

• Secretariat of War (1814)
• Secretariat of War and Navy (1818–1831)
• Ministry of War and Navy (1831–1924)
• Ministry of War and Ministry of Navy (1924–1932)
• Ministry of National Defense – First Creation (1932)

• Ministry of War and Aviation and Ministry of Navy (1932)

• Ministry of National Defense – Second Creation (1932–present)

The main dependencies of the Ministry are:

• Subsecretariat of Defense: in charge of the defence policy

• National Academy of Political and Strategic Studies (ANEPE)

• Subsecretariat of the Armed Forces in charge of the administratives duties
• Joint Staff Command

• Military of Chile
• Defence Diplomacy

• República de Chile (1942). "VI. Poder Ejecutivo – Nómina de Gobernantes, Presidentes y Ministros desde la Independencia.". Manual del Senado. 1810–1942 (PDF) (in Spanish). Santiago de Chile: Imprenta Universitaria. (in Spanish)
• Valencia Avaria, Luis (1986). Anales de la República: textos constitucionales de Chile y registro de los ciudadanos que han integrado los poderes ejecutivo y legislativo desde 1810 (in Spanish) (2ª edición ed.). Santiago de Chile: Editorial Andrés Bello. (in Spanish)

• Official Website of the Ministry of Defense of Chile (in Spanish)