This article presents, for the first time in English, a translation of the two letters of the usurping emperor Magnus Maximus that are to be found within the Collectio Avellana (letters 39 and 40). The letters—from Maximus to the Emperor Valentinian II and from Maximus to Siricius, bishop of Rome—are each introduced with an extensive discussion of their subject matter, the circumstances of their composition, and their probable date. The article then considers possible reasons for these letters’ unusual survival; as letters of a usurping emperor, one would have expected them to be destroyed, and the article explores how we may understand their inclusion in the Collectio Avellana. Finally, the translations are given, with extensive commentary in their notes.