Firmicus Maternus was one of the last astrological writers of Late Antiquity (330s AD), during the rich period of early Neoplatonism and the rise of Christian emperors. Drawing on some of the earliest and most renowned Hellenistic astrologers, such as Nechepsō-Petosiris, Asclepius, and less known figures like Abraham, Firmicus is one of our most important sources of ancient astrological doctrine. Much of the Mathēsis is found nowhere else in surviving texts. This translation was especially designed for students who have been frustrated by the incompleteness and problems of prior editions. It contains an extensive Introduction with a glossary of special terms, ongoing astrological commentary, and over 100 tables and figures to illustrate Firmicus's principles and extensive chart examples. We hope that contemporary readers will gain a new appreciation for this classic text.