San Cristóbal Island (Spanish: Isla San Cristóbal) and named previously by the English as Chatham Island, is the easternmost island in the Galápagos archipelago, as well as one of the oldest geologically. It is administratively part of San Cristóbal Canton, Ecuador.
Its Spanish (and official Ecuadorian) name “San Cristóbal” comes from the patron saint of seafarers, St. Christopher. English speakers increasingly use that name in preference to the traditional English name of Chatham Island, derived from William Pitt, 1st Earl of Chatham.