Oxford Classical Texts, also known as Scriptorum Classicorum Bibliotheca Oxoniensis, provide authoritative, clear, and reliable editions of ancient texts, with apparatus criticus on each page. This five volume work is a new critical text edition of the only surviving ancient commentary on Plato's Timaeus, in which Proclus encompasses seven centuries of philosophical reflection on Plato's cosmology. For many authors belonging to the Platonic tradition, Proclus' commentary is the only extant source. For late Neoplatonic authors such as Proclus, writing commentaries on works by Plato and others was in fact a way to present their own highly original philosophical doctrines. Apart from being an important source text for the historiography of philosophy, this commentary on the Timaeus thus also provides a unique access way to Proclus' own Neoplatonic views on cosmology, theology, physics, and metaphysics. This new edition is based on a thorough re-examination of the entire manuscript tradition, which has led to a complete understanding of the relation between all extant manuscripts, including the Paris palimpsest BNF Supplément grec 921, belonging to the so-called 'collection philosophique' (9th century). On the basis of digitally enhanced UV photos, the scriptio inferior of this palimpsest (containing parts of books IV and V) was made nearly fully accessible. The study of the manuscript tradition and the apparatus fontium take stock of more than 100 years of study of this circumstantial text. The edition of the text is preceded by a substantial introduction, and followed, for each book, by the edition of the scholia to the text. The final volume also comprises an edition of the remaining fragments of the lost part of the text, including an Arabic fragment, edited by Rüdiger Arnzen.