Prester John (Latin: Presbyter Johannes) is a legendary Christian patriarch and king popular in European chronicles and tradition from the 12th through the 17th centuries. He was said to rule over a Nestorian (Church of the East) Christian nation lost amid the Muslims and pagans of the Orient. The accounts are varied collections of medieval popular fantasy, depicting Prester John as a descendant of the Three Magi, ruling a kingdom full of riches, marvels and strange creatures.
At first Prester John was imagined to reside in India; tales of the Nestorian Christians' evangelistic success there and of Thomas the Apostle's subcontinental travels probably provided the first seeds of the legend. After the coming of the Mongols to the Western world, accounts placed the king in Central Asia and eventually Portuguese explorers convinced themselves that they had found him in Ethiopia.
Though its immediate genesis is unclear, the legend of Prester John drew strongly from earlier accounts of the Orient and of Westerners' travels there. Particularly influential were the stories of St. Thomas the Apostle's proselytising in India, as recorded in the third-century work known as the Acts of Thomas, and reports of the Church of the East in Greater Persia. The Church of the East, also called the Nestorian church, had gained a wide following in Eastern nations and engaged the Western imagination as an assemblage both exotic and familiarly Christian. Particularly inspiring were the Nestorians' missionary successes among the Mongols and Turks of Central Asia; René Grousset (1970) suggested that one of the seeds of the story may have come from the Keraites, which had thousands of its members converted to Nestorian Christianity shortly after the year 1000. By the 12th century Keraite rulers were still following a custom of bearing Christian names, which may have fueled the legend.