Thucydides’ reception in the 19th century is a key moment for modern historical thought. This was a period when history was becoming institutionalized as a university discipline, and this chapter shows how Thucydides was invoked as a predecessor by a number of major figures in the field. The chapter also explores why this was the case, drawing attention to the paradox that this invocation of Thucydides entailed: how did a discipline that was seeking to establish itself as ‘modern’ find legitimacy in this ancient text? And how did this influence the way in which Thucydides’ historical project was read and understood?