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 Oceania in the west and the Americas in the east. At approximately 165 million square kilometers in surface area, the Pacific Ocean covers more than 30 percent of Earth's surface, an area larger than that of all the world's landmasses combined. The Mariana Trench, located in the western Pacific, is the deepest known point on the planet, reaching a depth of nearly 11,000 meters below sea level.

The Pacific Ocean contains tens of thousands of islands, far more than any other ocean. These islands are distributed across three broad cultural regions known as Melanesia, Micronesia, and Polynesia. The waters of the Pacific are home to a remarkable diversity of marine life, including coral reefs in the tropical regions and large populations of whales, sharks, and tuna in cooler waters. Strong ocean currents, such as the Kuroshio in the western Pacific and the California Current along the eastern margin, help redistribute heat across the basin and shape the climates of nearby continents.

Human exploration of the Pacific has a long history. Polynesian navigators crossed vast distances using stars, swells, and the flight patterns of seabirds long before European mariners arrived. In the sixteenth century, Ferdinand Magellan's expedition became the first known European voyage to cross the ocean, and he gave it the name Pacific because of the relatively calm waters his ships encountered after rounding the tip of South America.
