This thesis examines the literary representation of the Pannonian emperor Valentinian I (364-375) in two different types of source dated to the fourth and fifth centuries AD. More specifically, it analyses how literary sources which were contemporaneous with Valentinian's reign (Symmachus' imperial panegyrics; and imperial legislation) and which promoted the 'official' view of Valentinian's regime, were received and interpreted in the later historical sources for the emperor's reign (namely, Ammianus Marcellinus' Res Gestae; and the histories of the Christian historians Tyrannius Rufinus, Paulus Orosius, Socrates Scholasticus, Sozomen and Theodoret). By analysing three themes (dynastic, military and religious) which were prominent in both forms of representation, this thesis explores how and why these 'contemporary' and 'historical' representations of the emperor differed, and asks what the interaction of these sources can tell us about the literary representation of Valentinian more generally.