Prior to the destruction of the Jerusalem temple in 70 CE, Jewish social organization and ritual leadership in ancient Palestine was defined by sectarianism, in which coherent Jewish groups maintained competing beliefs about theology and practice. The centuries following the destruction saw the rise of the rabbinic movement, which produced extensive literary corpuses that occasionally make reference to the rabbis’ sectarian predecessors. This thesis explores the historical nature of the relationship between the rabbis and sects as well as the rabbinic literary construction of the sects and sectarian past. In the first chapter, I argue that the sects largely faded from the Judean landscape before the rabbinic movement emerged, even as Jewish sectarianism lived on in rabbinic memory. The subsequent chapters investigate the evolving rabbinic literary portrayal of the sects. I suggest that the rabbis’ depiction of the sectarian past shifted in response to the rabbis’ growing authority and relationship to emerging Christianity. Seeking to chart a new approach in a world in which they were largely unknown, the early rabbis (c. 70-220 CE) displayed little tolerance for both past and present outsiders and therefore avoided identification with the sects. However, as the rabbinic project grew increasingly established and distinct from competing movements, the later rabbis (c. 220-700 CE) began to link themselves to certain sects in order to bolster their historical legitimacy. This analysis seeks to capture fundamental aspects of the process of rabbinic identity-formation, shedding light on the self-definition and origination of the movement that remains the basis of Jewish practice to this day.