The Commentary of Albertus Magnus on Book I of Euclid’s Elements of Geometry is the third in Lo Bello’s series on the Elements. Lo Bello provides the first modern translation of a key Latin text of the Elements in the Middle Ages, the commentary of the Dominican scholastic philosopher Albertus Magnus (d.1280), the teacher of Thomas Aquinas. The volume includes a translation, notes on the translation, and a critical examination of the mathematical content of the three commentaries on Euclid’s Elements of Geometry thus far treated in this series.