This article explores the historical and conceptual relationships between themes of conspiracy, secrecy and securitization, firstly through a general schematic discussion of their interconnections, and then through a specific focus on the polemics and strategies of the French Bourbon Restoration period (1814-1830). The conspiracist visions of this period are contextualized by relating them to longer-term evolutions in conceptions of the state and of politics, and to the impact of the French Revolution. Comparisons are drawn between the strategies of the Right, focusing on the idea of revolutionary conspiracy and generally linked to a governmentalist agenda, and of the Left, focusing on a vision of Jesuit or theocratic conspiracy and usually oppositional in character. The final section of the article analyses the denunciations of the Jesuits in greater detail, through the lens of a model of securitization. Emphasis is placed on the ways in which denouncers of Jesuit conspiracy combined historical argument with legal attacks on the Jesuits’ corporate existence, on the fluidity of their conceptions of the conspiratorial threat, and on the ways in which denunciations of Jesuit conspiracy reflect broader liberal anxieties over power and identity in an age of political transformation.