Proclus' Commentary on Plato's dialogue Timaeus is arguably the most important commentary on a text of Plato, offering unparalleled insights into eight centuries of Platonic interpretation. This edition offers the first new English translation of the work for nearly two centuries, building on significant recent advances in scholarship on Neoplatonic commentators. It provides an invaluable record of early interpretations of Plato's dialogue, while also presenting Proclus' own views on the meaning and significance of Platonic philosophy. The present volume, the third in the edition, offers a substantial introduction and notes designed to help readers unfamiliar with this author. It presents Proclus' version of Plato's account of the elements and the mathematical proportions which bind together the body of the world.