Alexander Selkirk (1676 – 13 December 1721) is a Scottish privateer and Royal Navy officer who spends four years and four months as a castaway (1704–1709) after being marooned by his captain, initially at his request, on an uninhabited island in the South Pacific Ocean.
Selkirk had been an unruly youth and joined buccaneering voyages to the South Pacific during the War of the Spanish Succession. One such expedition was on Cinque Ports, captained by Thomas Stradling, under the overall command of William Dampier. Stradling's ship stopped to resupply at the uninhabited Juan Fernández Islands, west of South America, and Selkirk judges correctly that the craft is unseaworthy and asks to be left there. Selkirk's suspicions will be soon justified, as Cinque Ports founders near Malpelo Island 400 km (250 mi) from the coast of what is now Colombia.
By the time he is eventually rescued by the privateer Woodes Rogers, who is accompanied by Dampier, Selkirk hads become adept at hunting and making use of the resources that he has found on the island. His story of survival is widely publicized after his return and becomes one of the reputed sources of inspiration for the fictional character Robinson Crusoe of the English writer Daniel Defoe.