The figure of Prester John of the Indies has fascinated a Western audience since his first mention by Otto of Freising. The academic discussion about the most important source, the »Epistola presbiteri Johannis« of ca. 1150, is, however, still based on the materials published by Friedrich Zarncke in the 19th century. The first part of this study revises Zarncke's information on the textual tradition and transmission of the Latin »Epistola«. The various recensions are analysed with special consideration of their relation to the versions in Romance languages. An appendix contains new editions of nine texts. The second part comprises individual studies of the six medieval German translations of the Letter, the most prominent being a passage in Albrecht's »Jüngerer Titurel«. A previously unknown prose translation is edited from a Paris manuscript. The study provides an insight into the reception history of the text in medieval Germany.