The Pacific Ocean theater of World War II was a major theater of the Pacific War, the war between the Allies and the Empire of Japan. It was defined by the Allied powers' Pacific Ocean Area command, which included most of the Pacific Ocean and its islands, while mainland Asia was excluded, as were the Philippines, the Dutch East Indies, Borneo, Australia, most of the Territory of New Guinea, and the western part of the Solomon Islands.

It officially came into existence on March 30, 1942, when US Admiral Chester Nimitz was appointed Supreme Allied Commander Pacific Ocean Areas.^[1] In the other major theater in the Pacific region, known as the South West Pacific theater, Allied forces were commanded by US General Douglas MacArthur. Both Nimitz and MacArthur were overseen by the US Joint Chiefs and the Western Allies Combined Chiefs of Staff (CCoS).

Most Japanese forces in the theater were part of the Combined Fleet (連合艦隊, Rengō Kantai) of the Imperial Japanese Navy (IJN), which was responsible for all Japanese warships, naval aircraft, and marine infantry units. The Rengō Kantai was led by Admiral Isoroku Yamamoto, until he was killed in an attack by U.S. fighter planes in April 1943.^[2] Yamamoto was succeeded by Admiral Mineichi Koga (1943–44)^[2] and Admiral Soemu Toyoda (1944–45).^[3] The General Staff (参謀本部, Sanbō Honbu) of the Imperial Japanese Army (IJA) was responsible for Imperial Japanese Army ground and air units in Southeast Asia and the South Pacific. The IJN and IJA did not formally use joint/combined staff at the operational level, and their command structures/geographical areas of operations overlapped with each other and those of the Allies.

In the Pacific Ocean theater, Japanese forces fought primarily against the United States Navy, the U.S. Army, which had 6 Corps and 21 Divisions, and the U.S. Marine Corps, which had only 6 Divisions. The United Kingdom (British Pacific Fleet), New Zealand, Australia, Canada, and other Allied nations, also contributed forces.

• Pacific theater
  • Attack on Pearl Harbor 7 December 1941^[4]
  • Battle of Wake Island 7–23 December 1941^[5]
  • Philippines campaign 8 December 1941 – 8 May 1942
    • Battle of Bataan
    • Battle of Corregidor
  • Battle of Ambon
  • Battle of Timor
  • Battle of Rabaul
  • Battle of the Java Sea
  • Bombing of Darwin
  • Battle of the Coral Sea 4–8 May 1942
  • Doolittle Raid 18 April 1942^[4]
  • Battle of Midway 4–7 June 1942^[4]
  • Guadalcanal campaign 7 August 1942 to 9 February 1943
    • Battle of Savo Island
    • Battle of Cape Esperance
    • Second Naval Battle of Guadalcanal
    • Battle of Tassafaronga
  • New Guinea campaign
  • Solomon Islands Campaign
  • Battle of the Bismark Sea
  • Gilbert and Marshall Islands campaign 1943–44
    • Makin Island raid 17–18 August 1942^[6]
    • Battle of Tarawa 20 November 1943^[4]
    • Battle of Makin 20–23 November 1943
    • Battle of Kwajalein 14 February 1944^[7]
    • Battle of Eniwetok 17 February 1944^[8]
  • Attack on Truk Island 17–18 February 1944
  • Mariana and Palau Islands campaign 1944
    • Battle of Saipan 15 June 1944^[9]
    • Battle of the Philippine Sea 19–21 June 1944^[10]
    • Battle of Guam 21 July 1944^[11]
    • Battle of Tinian 24 July 1944^[11]
    • Battle of Peleliu 15 September 1944^[12]
    • Battle of Angaur 17 September 1944^[12]
    • Battle of Leyte 17 October 1944
    • Battle of Luzon 9 January 1945
  • Battle of Iwo Jima 19 February 1945^[4]
  • Battle of Okinawa 1 April 1945^[4]
• North Pacific theater
  • Aleutian Islands Campaign 1942–43
  • Battle of the Komandorski Islands 26 March 1943^[4]

• Cressman, Robert J. (2000), The Official Chronology of the U.S. Navy in World War II, Annapolis, MD: Naval Institute Press, ISBN 1-55750-149-1.
• Drea, Edward J. (1998), In the Service of the Emperor: Essays on the Imperial Japanese Army, NB: University of Nebraska Press, ISBN 0-8032-1708-0.
• Hakim, Joy (1995), A History of Us: War, Peace and All That Jazz, New York: Oxford University Press, ISBN 0-19-509514-6.
• Kafka, Roger; Pepperburg, Roy L. (1946), Warships of the World, New York: Cornell Maritime Press.
• Miller, Edward S. (2007), War Plan Orange: The U.S. Strategy to Defeat Japan, 1897–1945, US Naval Institute Press, ISBN 978-1-59114-500-4.
• Ofstie, Ralph A. (1946). The Campaigns of the Pacific War. Washington, DC: United States Government Printing Office..
• Potter, E. B.; Nimitz, Chester W. (1960), Sea Power, Prentice-Hal.
• Silverstone, Paul H. (1968), U.S. Warships of World War II, Doubleday & Co.
• Toll, Ian W. (2011). Pacific Crucible: War at Sea in the Pacific, 1941–1942. New York: W. W. Norton.
• ——— (2015). The Conquering Tide: War in the Pacific Islands, 1942–1944. New York: W. W. Norton.
• ——— (2020). Twilight of the Gods: War in the Western Pacific, 1944–1945. New York: W. W. Norton.