After sailing through the dangerous straits below South America that now bear his name, Portuguese navigator Ferdinand Magellan enters the Pacific Ocean with three ships, becoming the first European explorer to reach the Pacific from the Atlantic. On 20 September 1519, Magellan set sail from Spain in an effort to find a western sea route to the rich Spice Islands of Indonesia. In command of five ships and 270 men, Magellan sailed to West Africa and then to Brazil, where he searched the South American coast for a strait that would take him to the Pacific. He searched the Rio de la Plata, a large estuary south of Brazil, for a way through; failing, he continued south along the coast of Patagonia.

At the end of March 1520, the expedition set up winter quarters at Port St. Julian. On Easter day at midnight, the Spanish captains mutinied against their Portuguese captain, but Magellan crushed the revolt, executing one of the captains and leaving another ashore when his ship left St. Julian in August. On 21 October, he finally discovered the strait he had been seeking. The Straits of Magellan, as it became known, is located near the tip of South America, separating Tierra del Fuego and the continental mainland. Only three ships entered the passage; one had been wrecked and another deserted. It took 38 days to navigate the treacherous strait, and when clear ocean was sighted at the other end Magellan wept with joy. His fleet accomplished the westward crossing of the ocean in 99 days, crossing waters so strangely calm that the ocean was named "Pacific," from the Latin word pacificus, meaning "tranquil."

By the end, the men were out of food and chewed the leather parts of their gear to keep themselves alive. On 6 March 1521, the expedition landed at the island of Guam. Ten days later, they dropped anchor at the Philippine island of Cebu – they were only about 400 miles from the Spice Islands. Magellan met with the chief of Cebu, who after converting to Christianity persuaded the Europeans to assist him in conquering a rival tribe on the neighbouring island of Mactan. In fighting on 27 April, Magellan was hit by a poisoned arrow and left to die by his retreating comrades. After Magellan's death, the survivors, in two ships, sailed on to the Moluccas and loaded the hulls with spice. One ship attempted, unsuccessfully, to return across the Pacific. The other ship, the Vittoria, continued west under the command of Basque navigator Juan Sebastian de Elcano. The vessel sailed across the Indian Ocean, rounded the Cape of Good Hope, and arrived at the Spanish port of Sanlucar de Barrameda on 6 September 1522, becoming the first ship to circumnavigate the globe.