Immanuel Tremellius (1510-1580) was one of the most significant and important theological scholars of the Reformation, whose influence lasted well into the eighteenth century. Following his conversion to Christianity from Judaism, he rose to prominence in the mid-sixteenth century as a professor of Hebrew and Old Testament studies, teaching in numerous highly prestigious Reformed academies and universities across northern Europe. This study of Tremellius' life and works, the first full-length work since the late nineteenth century, provides a chronological framework that traces his spiritual progression from Judaism through Catholicism and on to Protestantism, as well as his physical progression across Europe. Within this structure is woven a broader contextual examination Tremellius' place within the intellectual history of the Reformation, both as a Christian scholar and a converted Jew. The book concludes with a detailed look at Tremellius' two most important publications, his translation of the New Testament from Syriac into Latin of 1569, and his translation of the Old Testament from Hebrew in to Latin of 1575-1579.It is on these two books that his long-term international reputation rests, and as such much is revealed by looking at their composition, the figures to whom they were dedicated, the choice of language, their appearance, publishing history and the roles they were intended to fill. Encompassing issues of theology, education and conversion, this book not only provides a fascinating biography of one of the most neglected biblical scholars of the sixteenth century, but also sheds much light on the often ambiguous attitude of Christians towards Jews and Jewish scholarships during the Reformation.