The Strait of Magellan (Spanish: Estrecho de Magallanes), also called the Straits of Magellan, is a navigable sea route in southern Chile separating mainland South America to the north and Tierra del Fuego to the south. The strait is considered the most important natural passage between the Atlantic and Pacific oceans. It was discovered and first traversed by the Spanish expedition of Ferdinand Magellan in 1520, after whom it is named. Prior to this, the strait had been navigated by canoe-faring indigenous peoples including the Kawsqar.

Magellan's original name for the strait was Estrecho de Todos los Santos ("Strait of All Saints"). The King of Spain, Emperor Charles V, who sponsored the Magellan-Elcano expedition, changed the name to the Strait of Magellan in honor of Magellan.The route is difficult to navigate due to frequent narrows and unpredictable winds and currents. Maritime piloting is now compulsory. The strait is shorter and more sheltered than the Drake Passage, the often stormy open sea route around Cape Horn, which is beset by frequent gale-force winds and icebergs. Along with the Beagle Channel, the strait was one of the few sea routes between the Atlantic and Pacific before the construction of the Panama Canal.

John Williams Wilson (1798–1857), also known as Juan Guillermos, was an English-Chilean sailor and politician. Born in Bristol, he entered the newly founded Chilean navy in 1824 and rose to the rank of commander. He was appointed governor of Talcahuano (1849–1855). He supervised construction of Fuerte Bulnes in 1843, which the government intended for a settlement at the Strait of Magellan. Puerto Williams, founded in 1953, was named for the naval commander.