Most scholars view Orosius of Braga as a writer of history and a zealous partisan of Augustine and Jerome. In this dissertation, I re-examine Orosius' political activity and argue that he is an independent political actor who should be understood in the backdrop of Spanish ecclesiastical politics. The three body chapters examine, respectively, Orosius' publication of the Commonitorium, Orosius' anti-Pelagian activity, and Orosius' efforts to bring the relics of Stephen to the West. The Commonitorium has most commonly been seen as a document meant to inform Augustine about Priscillianism and Origenism so that Augustine could help Orosius argue against heresy. Instead, I argue that the Commonitorium and Augustine's reply are meant to be public documents intended to raise the status of the bishops of Galicia by linking them to a higher status bishop. Orosius' anti-Pelagian efforts in Jerusalem have been seen as unsuccessful and fueled by an impetuous zeal. In my analysis, I find that Orosius' accusations against Pelagius serve to solidify Augustine's opinions on original sin as the standards by which Pelagius should be judged. While Pelagius was acquitted, this step makes Orosius an essential strategic factor in Augustine's ultimate victory in the Pelagian controversy. Finally, the relics of Stephen have largely been understood by scholars to be intended to help the church of Braga deal with barbarian occupation. By examining how bishops use and write about the relics in Jerusalem, North Africa, and Minorca, I make the argument that the relics were more likely intended to restore confessional unity in the religiously polarized region of Galicia. Finally, I conclude the dissertation by proposing a new model of ecclesiastical conflict, drawn from modern political science. This model will provide historians of ecclesiastical politics more powerful and precise tools to describe the construction and contestation of orthodoxy.