This study examines the rise, development, and crisis of theological encyclopaedia in nineteenth-century Germany. As introductory textbooks for theological study in the university, works of theological encyclopaedia addressed the pressing questions facing theology as a ‘science’ (Wissenschaft), a rigorous, critical discipline deserving of a seat in the modern university. The project of theological encyclopaedia, I argue, functioned as the place where theological reflection and the requirements of the institutional setting in which that reflection occurred—here the German university—converged. I explore its roots as a pioneering idealist model for organizing knowledge in the German university system in the late eighteenth century. I focus especially on Friedrich Schleiermacher (1768–1834), the father of modern Protestantism and principal intellectual architect of the University of Berlin (1810). Schleiermacher’s programme transformed the scholarly theological enterprise into one defined in terms of science. That transformation laid the groundwork for the later historicization of theology, which I investigate in the two predominant ‘schools’ of German university theology in the middle of the nineteenth century, the Hegelian ‘speculative’ school and ‘mediating theology’ (Vermittlungstheologie). Among the latter, I emphasize the remarkable international influence of the Swiss-German Karl Hagenbach (1801–74), whose theological encyclopaedia was among the most widely read theological books in German-speaking Europe from the 1830s through World War I. Finally, I analyze the project’s downfall in the context of Wilhelmine Germany and the Weimar Republic, beset by radical disciplinary specialization, a crisis of historicism, and the attacks of dialectical theology. Throughout, I contend that theological encyclopaedia represented the institutionalization of the idea of theology as science, which furnishes an explanatory grid for understanding the relationship between theology and the university. The project resulted in a powerful synthesis that fundamentally shaped the reigning theological paradigms in nineteenth-century Germany and beyond.