Barlaam and Josaphat (Latin: Barlamus et Iosaphatus) are two legendary Christian martyrs and saints, based ultimately on the life of the Buddha. It tells how an Indian king persecuted the Christian Church in his realm. When astrologers predicted that his own son would some day become a Christian, the king imprisoned the young prince Josaphat, who nevertheless met the hermit Saint Barlaam and converted to Christianity. After much tribulation the young prince's father accepted the true faith, turned over his throne to Josaphat, and retired to the desert to become a hermit. Josaphat himself later abdicated and went into seclusion with his old teacher Barlaam. The tale derives from a second to fourth century Sanskrit Mahayana Buddhist text, via a Manichaean version, then the Arabic Kitab Bilawhar wa-Yudasaf (Book of Bilawhar and Yudasaf), current in Baghdad in the eighth century, from where it entered into Middle Eastern Christian circles before appearing in European versions. The two were entered in the Eastern Orthodox calendar with a feast-day on 26 August, and in the Roman Martyrology in the Western Church as "Barlaam and Josaphat" on the date of 27 November.
The story of the two Indian saints was ultimately derived, through a variety of intermediate versions (Arabic and Georgian), from the life story of the Buddha.
Wilfred Cantwell Smith (1981) traced the story from a 2nd to 4th century Sanskrit Mahayana Buddhist text, to a Manichaean version, which then found its way into Muslim culture as the Arabic Kitab Bilawhar wa-Yudasaf (Book of Bilawhar and Yudasaf), which was current in Baghdad in the 8th century.