This history of the concept of fact reveals that the fact-oriented practices of German physicists and historians derived from common origins. The concept of fact became part of the German language remarkably late. It gained momentum only toward the end of the eighteenth century. I show that the concept of fact emerged as part of a historical knowledge tradition, which comprised both human and natural empirical study. Around 1800, parts of this tradition, including the concept of fact, were integrated into the epistemological basis of several emerging disciplines, including physics and historiography. During this process of discipline formation, the concept of fact remained fluid. I reveal this fluidity by unearthing different interpretations and roles of facts in different German contexts around 1800. I demonstrate how a fact-based epistemology emerged at the University of Göttingen in the late eighteenth century, by focusing on universal historian August Ludwig Schlözer and the experimentalist Georg Christoph Lichtenberg. In a time of scientific and political revolutions, they regarded facts as eternal knowledge, contrasting them with short-lived theories and speculations. Remarkably, Schlözer and Lichtenberg construed facts as the basis of Wissenschaft , but not as Wissenschaft itself. Only after 1800, empirically minded German physicists and historians granted facts self-contained value. As physics and historiography became institutionalized at German universities, the concept of fact acquired different interpretations in different disciplinary settings. These related to fact-oriented research practices, such as precision measurement in physics and source criticism in historiography.