Can Jewish sources be used as an archive for the history of a Nubian diaspora in Islamic Egypt? This paper is a study of all the Nubian women, children, and men who are identified in a large corpus of manuscripts now called the Cairo geniza, which were preserved in a synagogue in Fustat (Old Cairo) and written primarily in a Judeo-Arabic, a variety of Arabic written in the Hebrew script. It argues that the collective biography of these individuals illustrates a process by which many Nubian people were coercively integrated into the Egyptian Jewish community in ways that ultimately erased their Nubian-ness and re-inscribed them as Jews who were recognized and protected subjects of the Fatimid caliphate and Ayyubid sultanate. In geniza sources, Nubian people almost always appear as either enslaved or freed persons in bills of sale and communal records. Their presence reflects the geography of the transregional slave trade to Cairo in this period when Nubians were the largest single group alongside Indians, Bejas, Greeks, and those born into slavery within Egypt. Manumission deeds and communal records demonstrate that some Nubians were freed by their Jewish owners. In Jewish law, a person’s manumission also affected their full religious conversion to Judaism. Freed Nubians, both women and men, sometimes became the parents of freeborn Jewish children. By the second- or third-generation, there are no traces of Nubian-ness or slave-status in the names or descriptions of Egyptian Jews despite the widespread presence of enslaved Nubians in Jewish households. I argue that this underscores how Jewish law functioned in this context to deracinate enslaved people and to reinstate them as licit members of the Jewish community and the Islamic imperium. The second part of the paper juxtaposes geniza sources with contemporaneous Arabic documents and asks to what extent the “Nubian-Jewish” history may illustrate a larger phenomenon through which African groups from outside of Islamic territories (dār al-Islām) were forcibly absorbed into Egyptian society. In Islamic law and practice, the umm walad (mother of child) was a legal category for enslaved women who gave birth to their Muslim owners’ free-born children. Muslim men also freed and married enslaved women who were or became mothers of free children. Both of these strategies, as in Jewish laws of conversion and slavery, had the effect of erasing the presence of Nubian people and culture from the written records used by historians.