Porto Santo Island is a Portuguese island 43 kilometres (27 mi) northeast of Madeira Island in the North Atlantic Ocean; it is the northernmost and easternmost island of the archipelago of Madeira, located in the Atlantic Ocean west of Europe and Africa.
It appears that some knowledge of Atlantic islands, such as Madeira, existed before the discovery and settlement of these lands, as the islands appear on maps as early as 1339. From a portolan dating to 1351, and preserved in Florence, Italy, it would appear that the islands of Madeira had been discovered long before being claimed by the Portuguese expedition of 1418. In Libro del Conocimiento (1348?1349), a Castilian monk also identified the location of the islands in their present location, with the names Leiname (modern Italian legname, cognate of Portuguese madeira, "wood"), Diserta and Puerto Santo. Indeed, the move by Portugal to claim the Madeiran islands was probably a response to Spain's efforts at the time to claim and subdue the Canary Islands.
However, humans never recorded the discovery of Porto Santo Island or the other Madeira islands until 1418, when Porto Santo was accidentally discovered after captains were storm blown into its sheltered harbor. They were in the service of Infante Henrique of Portugal. Joâo Gon?alves Zarco and Tristâo Vaz Teixeira had been ordered by King John I to discover new territory west of Africa and had been sent off-course by a storm while making the volta do mar westward swing return voyage. The island's name Porto Santo (en: "Holy Harbour") was derived from the sailors' stories of their discovery of a sheltered bay during the tempest, which was interpreted as divine deliverance. The first Portuguese settlers arrived in the 1420s.
Bartolomeu Perestrelo, a member of the team that later explored the Madeira Islands, became the first Captain-donatório of Porto Santo, by royal award in November 1445. It was he who released a female rabbit that had littered on the voyage, with her offspring, which multiplied catastrophically in a xeric island ecosystem that had evolved in isolation and had never known a flightless mammal. The loss of the native flora laid the island slopes open to erosion and colonization by European weeds that accompanied the settlers. As a result, "the Porto Santo of 1400 is as lost to us as is the world before the Noachian flood".
During the first centuries of settlement, life on Porto Santo was harsh, owing to the scarcity of potable water and the depredations of feral rabbits; there were also constant attacks by Barbary Coast pirates and French privateers.
The New World explorer Christopher Columbus married the Portuguese noblewoman Filipa Moniz Perestrelo, the daughter of Bartolomeu Perestrelo. For a while they lived on Porto Santo. The home is now a museum.