My dissertation explores the transitions from slave to citizen in Iran during the late nineteenth and early twentieth centuries, seen through the trajectories of enslaved and freed peoples from the Caucasian and East African slave trades. Though ethnicity has been privileged in Iranian social history, I argue that race served an important role for defining enslaved populations in Iran, and Iranians readily identified slaves with racial labels. These racialized identities proved problematic in the aftermath of abolition, when government-led processes and social stigma demanded a reconstruction of ethnic identities for these populations. I analyze the gradual erasure of slavery from Iranian historical memory and discuss the role of abolition in the nation-building process. Finally, I present a social history of forced migrations and minorities in modern Iran, with special attention to the historical complexities of incorporating regional and racial peripheries in the nation. From the 1880s to the 1940s, as both nationalist and abolitionist efforts came to a head, government officials, journalists, secular intellectuals, and clerics negotiated or ignored racial diversity in order to assimilate formerly enslaved peoples. Each chapter of the dissertation examines a crucial period, from the last decades of legal slavery, to the dismantling of the institution in 1928, to the subsequent reverberations of abolition. The epilogue, centered upon the 1980s, explores ideological erasures of domestic slavery in the early years of the Islamic Republic and the Iran-Iraq War. My research on the racialization of group identities and its legacy expands current discourse on slavery and abolition to Iran and challenges popular and academic notions of Iranian ethnic diversity.