This thesis argues that Byzantine empress Theodora (d. 548 CE) and al-Khayzuran (d. 789 CE), mother and wife of Abbasid caliphs, manipulated and challenged existing expectations to exercise political, religious, and economic power. They achieved upward mobility through the use of their female bodies, first as slaves, then concubines, and then as wives, maternal-figures, and rulers. They exercised power: funding construction of religious buildings, offering charity to the poor, undertaking religious pilgrimages, protecting the weak, financing infrastructure improvements, and quelling political dissent. This comparison demonstrates that despite differences in time and place, the lives and depictions of Theodora and al-Khayzuran, and the gender expectations for imperial women in both the Byzantine Empire and Abbasid caliphate were similar. Both women rose to power during similar periods of transition and empire formation, resulting in comparably ambivalent representations of both female rulers by their contemporary writers. To investigate the reasons for and the nature of these similarities, this thesis analyzes sometimes hostile male authors' depictions of these women's political, religious, and economic actions. Male authors from late antiquity attempted to articulate appropriate behaviors for imperial women to emulate. Procopius, a sixth-century Byzantine historian, and al-Tabari, a ninth-century Abbasid historian, praised and criticized Theodora and al- Khayzuran, respectively, in their roles first as slaves and concubines, and later as wives, mothers, and rulers. John Malalas, a sixth-century Byzantine chronicler, and al-Masudi, a tenth-century Abbasid historian, portrayed the actions of the "ideal" female body as generosity towards the disenfranchised, providing public works of philanthropy, and maintaining the political dynasty. These expectations were not modeled after the lives of Empress Theodora and al-Khayzuran but from the memory of previous women who set the appropriate behaviors of piety and regality. This project deploys a gendered approach to read between the lines of Procopius, al-Tabari, Malalas, and al-Masudi to determine how these women were able to negotiate power as imperial leaders. This analysis aims to analyze gendered power structures and how they operated within Late Antique Byzantine and Abbasid societies.