The Philippine Sea is a marginal sea of the Western Pacific Ocean east of the Philippine Archipelago and the largest sea in the world, occupying an estimated surface area of 5 million square kilometers. The Philippine Sea Plate forms the floor of the sea. Its western border is the first island chain to the west, comprising the Ryukyu Islands in the northwest and Taiwan in the west. Its southwestern border comprises the Philippine islands of Luzon, Catanduanes, Samar, Leyte, and Mindanao. Its northern border comprises the Japanese islands of Honshu, Shikoku and Kyūshū. Its eastern border is the second island chain to the east, comprising the Bonin Islands and Iwo Jima in the northeast, the Mariana Islands in the due east, and Halmahera, Palau, Yap and Ulithi in the southeast. Its southern border is Indonesia's Morotai Island.

The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean in the south, and is bounded by the continents of Asia and Australia in the west and the Americas in the east.