This volume presents a critical edition, translation, and study of one of the most important works of medieval science, the Almagesti minor, the earliest Latin commentary on Ptolemy?s Almagest. This summary of the first half of the Almagest incorporated the astronomy of Islamic astronomers and altered Ptolemy?s work to make it accord with the author?s scientific ideals. The Almagesti minor had a profound effect upon astronomical writings throughout the 13th-15th centuries, including the work of Georg Peurbach, Johannes Regiomontanus, and many others. The Almagesti minor is one of the most important works of medieval astronomy. Probably written in northern France circa 1200, it is a Latin summary of the first six books of Ptolemy?s astronomical masterpiece, the Almagest. Also known to modern scholars as the ?Almagestum parvum?, the Almagesti minor provides a clear example of how a medieval scholar understood Ptolemy?s authoritative writing on cosmology, spherical astronomy, solar theory, lunar theory, and eclipses. The author incorporated the findings of astronomers of the Islamic world, such as al-Batt?n?, into the framework of Ptolemaic astronomy, and he altered the format and style of Ptolemy?s astronomy in order to make it accord with his own ideals of a mathematical science, which were primarily derived from Euclid?s Elements. The Almagesti minor had a profound effect upon astronomical writing throughout the 13th-15th centuries, including the work of Georg Peurbach and Johannes Regiomontanus. In this first volume of the Ptolemaeus Arabus et Latinus text series, Henry Zepeda offers not only a critical edition of this little-studied text, but also a translation into English, analysis of both the text and its geometrical figures, and a thorough study of the work?s origins, sources, and long-lasting influence. Henry Zepeda is a historian of science. He is a Teaching Fellow at Wyoming Catholic College, and he previously worked in the Ptolemaeus Arabus et Latinus project at the Bavarian Academy of Sciences and Humanities. His research is focused upon medieval mathematics and astronomy of the 12th to 15th centuries.