The Magellan expedition, also known as the Magellan-Elcano expedition, was a 16th-century Spanish expedition planned and led by Portuguese explorer Ferdinand Magellan. One of the most important voyages in the Age of Discovery—and in the history of exploration—its purpose was to cross the Atlantic and Pacific Oceans to open a trade route with the Moluccas, or Spice Islands, in present-day Indonesia. The expedition departed Spain in 1519 and returned there in 1522 led by Spanish navigator Juan Sebastián Elcano, who crossed the Indian Ocean after Magellan's death in the Philippines. Totaling 60,440 km, or 37,560 mi, the nearly three-year voyage achieved the first circumnavigation of Earth in history. It also revealed the vast scale of the Pacific Ocean and proved that ships could sail around the world on a western sea route.

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.