Geoffrey of Aspall, who died in 1287 and was master of Arts by 1262, was active at Oxford in the years 1255 to1265. He wrote commentaries on several Aristotelian works, and was certainly a major protagonist of the introduction of Aristotelian learning to Oxford. In particular, he produced a very extensive question-style commentary on Aristotle's Physics, which contains important discussions of the fundamental topics of Aristotle's natural philosophy, like matter, form, natural agency, causes, change, the infinite and the continuum, time, the eternity of the world, self-movers. Aspall's Physics commentary shows the influence of Grosseteste's metaphysics of light and of Roger Bacon's view on the physical role of intentional species, as well as a strong inclination to ontological realism.Aspall's commentary on Aristotle's Physics is edited here in two volumes, which together form the first critical edition of this work. The Latin text is accompanied by a facing English translation, and the text is extensively cross-referenced and provided with scholarly apparatus. The detailed introduction guides the reader through the intricacies of the textual transmission of Aspall's commentary, and also presents the main topics discussed in this commentary. The appendix to the edition makes available alternative versions of some sections of Aspall's commentary.