International Relations (IR) scholarship has long been informed, though often tacitly, by theories or philosophies of history. This chapter surveys theories of history, especially as they have shaped the field. We proceed as follows. First, we define philosophy or theory of history and briefly delineate its modern intellectual history. Second, we survey its shifting impact on disciplinary IR. From the early-twentieth century onward, we pay attention to philosophy of history tracking IR's interest in history as such: prominent early on, declining through the postwar period, and more recently reappearing, in proliferating variety. We close with a discussion of ways forward for theories and theorists of history in IR.