Saint Helena
The island was discovered in 1502 by the Portuguese admiral João da Nova, and he named it "Santa Helena" after Helena of Constantinople. The traditional date of this discovery was long thought to be 21 May, but the results of an investigation into the discovery published in 2015 concluded this date is probably wrong, the 3 May seeming to be historically more valid. Another theory holds that the island found by De Nova was actually Tristan da Cunha,  to the south, and that Saint Helena was discovered by some of the ships under the command of Estêvão da Gama on 30 July 1503.