Arsaces III was the King of Greater Armenia from 378 to 387 AD. As the elder son of King Pap, he and his brother, Vagarshak, were appointed as rulers of Armenia by the Roman Emperor Theodosius I. In 387, Emperor Theodosius signed a treaty with the Persian King Shapur III to partition Armenia. Unwilling to remain in the eastern part of the country under the rule of Zoroastrian Persia, Arshak relocated to the western, Byzantine-controlled sector. He was accompanied by all the Christian nakharars (nobles). Arshak III is often recognized as the last Armenian king to rule as a Roman vassal. During his reign, the territory he governed remained under Roman suzerainty in accordance with the Treaty of Acilisene.