Sefer Hakhmoni by the 10th-century Jewish polymath Shabbatai Donnolo is one of the first texts written in Hebrew in medieval Europe and one of the most important documents of the “Hebrew Renaissance” of Byzantine Jewry in southern Italy between the 9th and the 11th centuries. Written as a commentary on Sefer Yeîirah (Book of Formation, an anonymous text probably written in Palestine between the 3rd and the 6th centuries), Sefer Hakhmoni is in fact a much more complex work, consisting of biblical exegesis, astrology, medicine, a detailed analysis of the neo-Platonic idea of melothesia, and the correspondence between the elements of the microcosm and macrocosm. This volume offers the critical text, an annotated English translation, and a comprehensive introduction to Donnolo and his works.