Olympiodorus of Thebes is an important figure for the history of late antiquity. The few details of his life preserved as anecdotes in his History give glimpses of a career which embraced the skills of poet, philosopher, and diplomat. A native of Egypt, he had influence at the imperial court of Constantinople, among the sophists of Athens, and even outside the borders of the empire. His History (more correctly, his “materials for history”) is lost, surviving only as fragments in the narratives of Zosimus, Sozomen, and Philostorgius, and in the rich summary given by the ninth-century Byzantine patriarch Photius. These remains comprise the most substantial narrative sources for events in the western Roman Empire in the early fifth century. Besides its value as a source, the History is important as a monument to the vitality of the belief in the unity of the Roman Empire under the Theodosian dynasty. Olympiodorus wrote in Greek, and knowledge of his work is attested only in Constantinople, yet his political narrative, from 407 to 425, concerns only events in the western half of the empire. To understand the significance of these facts, it is necessary to set the composition of Olympiodorus's work in its proper context. Clarifying the date of publication is the first step toward this goal. Internal and external evidence suggests that the work was written in 440 or soon after, more than a decade later than the date of composition usually accepted. Taken with thematic emphases evident in the structure of the History, this revised dating explains why an eastern writer should have written a detailed account of western events in the early part of the century. Olympiodorus's account is a characteristic product of the highly literate class of eastern imperial civil servants, and of their genuine preoccupation with the relationship between the eastern and western halves of the Roman Empire at a time when both were threatened by the rise of the new Carthaginian power of the Vandals.