This article discusses the relationship between the papal Bull Unigenitus (1713) and the Catholic Enlightenment. The circumstances under which this controversial bull was received in the 18th century in Europe, and particularly in France, partially occasioned the construction of factions in many dynastic states-factions either pro-Unigenitus or pro-Augustinian (including but not limited to Jansenists). These factions, in turn, tailored their particular varieties of Catholic Enlightenment in the process of elaborating their respective positions concerning Unigenitus. This article synthesizes general trends in the present scholarship in order to underscore the importance of Unigenitus to the response of the Catholic Church to the Enlightenment. Because the fractures introduced into Catholic Europe by the bull were most acute during the early 18th century in France and the most formative and contentious factionalism is often presumed to have occurred before the suppression of the bull's most stalwart defenders-the Jesuits-between 1759 and 1773, this article focuses chiefly on the formative years of Catholic Enlightenment factionalism in the middle third of the 18th century before the suppression of the Jesuits.