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.

The Pacific War, sometimes called the Asia–Pacific War or the Pacific Theater, was the theater of World War II that was fought in eastern Asia, the Pacific Ocean, the Indian Ocean, and Oceania. It was geographically the largest theater of the war, including the vast Pacific Ocean theater, the South West Pacific theater, the Second Sino-Japanese War, and the Soviet–Japanese War.