The Pacific Ocean is the largest of the world's five oceans (followed by the Atlantic Ocean, Indian Ocean, Southern Ocean, and Arctic Ocean). It Ocean of water surrounds between the Southern Ocean, Asia, Australia, and the Western Hemisphere.

If we count its size, it has a total area of 155.557 million sq km. If we talk comparatively, it is about 15 times the size of the US and covers about 28% of the global surface. It has a total coastline of 135,663 km. The deepest point is Challenger Deep in the Mariana Trench which is about 10,924 meters. It contains: 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 Pacific Ocean is currently shrinking by roughly 2.5 centimetres per year on three sides which roughly average 0.52 square kilometres a year, due to the effects of plate tectonics. The Atlantic Ocean is increasing in size by contrast. Micronesia, Melanesia and Polynesia are the three groups in which the the islands entirely within the Pacific Ocean can be divided. Continental islands, high islands, coral reefs and uplifted coral platforms are the four basic type of islands found in pacific ocean.

The volume of the Pacific Ocean has been estimated at some 714 million cubic kilometers, represents about 50.1 percent of the world's oceanic water. Surface water temperatures in the Pacific can vary from -1.4 °C to about 30 °C near the equator. Because of abundant equatorial precipitation throughout the year, the water near the equator is less salty than that found in the mid-latitudes.

The El Niño Southern Oscillation (ENSO) affects weather conditions in the tropical and subtropical Pacific. Each particular basin has its own seasonal patterns as May is the least active month while September is the most active month. All the tropical cyclone basins are active during the month of November. In the arctic, icing from October to May and persistent fog occurs from June to December. The Pacific Ring of Fire is the world's foremost belt of explosive volcanism. It is named so after the several hundred active volcanoes that sit above the various subduction zones.

Herring, Salmon, Sardines, Snapper, Swordfish, Tuna and Shellfish are yielded in the shallower shoreline waters of the continents and the more temperate islands. Overfishing has become a serious problem in some areas.

The Pacific Ocean was sighted by Spanish explorer Vasco Nunez de Balboa early in the 16th century. He called it Mar del Sur which means South Sea. Pacific name was given by Portuguese explorer Ferdinand Magellan in 1521.