Early history (1502–1658)

Most historical accounts state that the island was sighted on 21 May 1502 by Galician navigator João da Nova sailing in the service of Portugal, and that he named it Santa Helena after Helena of Constantinople. A paper published in 2015 observes that 21 May is probably a Protestant rather than a Catholic or Orthodox feast day, and the date was first quoted in 1596 by Jan Huyghen van Linschoten, who was probably mistaken because the island was discovered several decades before the Reformation and the start of Protestantism. An alternative discovery date of 3 May is suggested as being historically more credible; it is the Catholic feast day of the finding of the True Cross by Saint Helena in Jerusalem, and cited by Odoardo Duarte Lopes and Sir Thomas Herbert.

Another theory holds that the island found by da Nova was actually Tristan da Cunha, 2,430 kilometres (1,510 mi) to the south, and that Saint Helena was discovered by some of the ships attached to the squadron of the Estêvão da Gama expedition on 30 July 1503 (as reported in the account of clerk Thomé Lopes). Thomé Lopes mapped St Helena's geographic position with reasonable accuracy when he quoted its distance and direction with respect to locations such as Ascension, Cape Verde, São Tomé and the Cape of Good Hope. The island's map location with respect to Ascension and the Cape of Good Hope was likewise described following the 1505 Portuguese expedition led by Francisco de Almeida.

When Linschoten arrived on 12 May 1589 he reported seeing carvings made by visiting seamen on a fig tree that were dated as early as 1510. The Portuguese probably planted saplings rather than mature trees, and for these to be sufficiently large by 1510 to carry carvings suggests the plants were shipped to the island and planted there some years earlier, possibly within a few years of discovery.

A third discovery story, told by the 16th century historian Gaspar Correia, holds that the island was found by the Portuguese nobleman and warrior Dom Garcia de Noronha, who sighted the island on his way to India in late 1511 or early 1512. His pilots entered the island onto their charts and it has been suggested that this event was likely decisive in leading to the utilization of the island as a regular stopover for rest and replenishment for ships en route from India to Europe, from that date until well into the seventeenth century An analysis has been published of the Portuguese ships arriving at St Helena in the period 1502-1613.

The Portuguese found the island uninhabited, with an abundance of trees and fresh water. They imported livestock, fruit trees and vegetables, and built a chapel and one or two houses. The long tradition that João da Nova built a chapel from one of his wrecked carracks has been shown to be based on a misreading of the records. They formed no permanent settlement, but the island was an important rendezvous point and source of food for ships travelling by Cape Route from Asia to Europe, and frequently sick mariners were left on the island to recover before taking passage on the next ship to call at the island.

Englishman Sir Francis Drake probably located the island on the final leg of his circumnavigation of the world (1577–1580). Further visits by other English explorers followed and, once Saint Helena's location was more widely known, English ships of war began to lie in wait in the area to attack Portuguese India carracks on their way home.

In developing their Far East trade, the Dutch also began to frequent the island. The Portuguese and Spanish soon gave up regularly calling at the island, partly because they used ports along the West African coast, but also because of attacks on their shipping, the desecration of their chapel and religious icons, destruction of their livestock, and destruction of plantations by Dutch and English sailors.

The Dutch Republic formally claimed Saint Helena in 1633, although there is no evidence that they ever occupied, colonised, or fortified it. By 1651, the Dutch had mainly abandoned the island in favour of their colony at the Cape of Good Hope.