The Pacific Ocean is the world's largest water body, occupying a third of the Earth's surface. The Pacific contains about 25,000 islands (more than the total number in the rest of the world's oceans combined), almost all of which are found south of the equator. The Pacific covers an area of 179.7 million square kilometres. It hich includes Bali Sea, Bering Sea, Bering Strait, Coral Sea, East China Sea, Gulf of Alaska, Gulf of Tonkin, Philippine Sea, Sea of Japan, Sea of Okhotsk, South China Sea, Tasman Sea, and other tributary water bodies.

The Portuguese explorer, Ferdinand Magellan, named this ocean 'Pacific', a derivative of Mare Pacificum, a Latin name meaning 'peaceful sea'. The Pacific Ocean was first sighted by Europeans, in early 16th century. Even amongst them, Spanish explorer Vasco Núñez de Balboa was the first.

The western Pacific has the lowest known point on Earth, the Challenger Deep in the Marianas Trench, 11,034 metres deep, a mile more than Mount Everest is high.

Earth's longest mountain range, more than 50,000 kilometres long, is the Mid-Ocean Ridge, extending from the Arctic Ocean to the Atlantic, skirting Africa, Asia and Australia, and crossing the Pacific to the west coast of North America. It is four times longer than the Andes, Rockies, and Himalayas combined.

The Pacific Ocean occupies approximately 46 percent of water surface on Earth and nearly 32 percent of Earth's total surface area. Its average depth is approximately 14,000 feet or 4,280 metres. This ocean is larger than all of Earth's land area combined. Water temperatures range from freezing nearer to the poles to about 30C (86F) near the equator.

Known to be the deepest, oldest and largest ocean on Earth, most of Pacific basin rim is circled with earthquakes areas and volcanoes. The world's longest reef is the Great Barrier Reef in Pacific Ocean, off the Australian coast.

The Pacific Ocean reaches its greatest east-west width at about 5ºN latitude, where it stretches for approximately 19,800 kilometres. There are more than 25,000 islands in the Pacific Ocean, more than in the rest four oceans, however the island of New Guinea, the second largest island in the world, is the largest landmass entirely within the Pacific Ocean. Almost all the smaller islands of Pacific Ocean lie between 30ºN and 30ºS, extending from Southeast Asia to Easter Island. Basically four types of islands are found in the Pacific Ocean - continental islands, high islands, coral reefs, and uplifted coral platforms. The coral islands in Pacific Ocean, called atolls, are formed on the top of submerged volcanoes by coral polyps.

The West Pacific (near Asia) is in the Eastern Hemisphere, while the East Pacific (near the Americas) is in the Western Hemisphere, the International Dateline crossing it  approximately midway. It is connected with Arctic Ocean by the Bering Strait and with Atlantic Ocean by the Drake Passage, Straits of Magellan and the Panama Canal. It is connected with the Indian Ocean by passages in the Malay Archipelago and between Australia and Antarctica.