In 323 BC, the Macedonian conqueror Alexander the Great died in Babylon. In his life, he conquered the powerful Achaemenid Persian Empire. With his death, however, he left the Macedonian Empire without an heir that could command the confidence and loyalty of the entire army. Shortly thereafter, the empire was torn apart between Alexander's ambitious generals. Seizing an opportunity in 312 BC, the Macedonian general Seleucus embarked on a daring journey to reclaim Babylon, laying the foundations for the Seleucid Empire in Mesopotamia. Eventually stretching from the Mediterranean Sea to Central Asia, this massive empire encompassed a diverse subject population, from indigenous Mesopotamians to Greek and Macedonian settlers. My research seeks to explore the strategies that the early Seleucids employed to legitimize and consolidate their rule in Mesopotamia. Despite the growing body of literature on the Seleucid Empire, scholars of Seleucid history have tended to overlook the crucial formative years of the empire as well as the disturbances in Achaemenid rule of Mesopotamia prior to the arrival of the Macedonians. My research argues that, to secure their authority, Seleucus I and Antiochus I negotiated with pre-existing social structures—namely, the Mesopotamian temple elite—and rearranged interpersonal networks to muster popular support and facilitate social cohesion under Seleucid rule. To carry out the investigation, this research analyzes cuneiform documents, archaeological findings, and literary accounts by Greek and Roman authors.