Department of the Pacific (MarPac) was a United States Marine Corps ground training and administrative command established on 15 November 1920, which was responsible for the administration, training and equipment of the Marine Corps Units on the West Coast, 14th Naval District (Hawaii and outlying Pacific islands), 16th Naval District (the Philippines), 17th Naval District (Alaska and Aleutian Islands) and Marine Forces in Northern China (China Marines).

[1] The Department of the Pacific was activated as Marine Corps subheadquarters on 15 November 1920 in San Francisco with former Commandant of the Marines, Major general George Barnett, in command.

Department of the Pacific administered all marine units and activities on the West Coast of the United States include Supply depots in San Francisco.

[1] Following the end of War, responsibilities of Department of the Pacific were expanded to administration of all non Fleet Marine Force units in the Pacific Ocean Area.

Department of the Pacific was deactivated on 1 July 1960 and its responsibilities were transferred to Fleet Marine Force Pacific and Headquarters Marine Corps.