The article examines the inaugural encounter of the Greek theory of tyranny and the Roman institution of dictatorship. Although the twentieth century is credited for fusing the tyrant and the dictator into one figure/concept, I trace the origins of this conceptual synthesis in a much earlier historical period, that of the later Roman Republic and the early Principate, and in the writings of two Greek historians of Rome, Dionysius of Halicarnassus and Appian of Alexandria. In their histories, the traditional interest (...) in the relationship between the king and the tyrant is displaced by a new curiosity about the tyrant and the dictator. The two historians placed the two figures alongside one another and found them to be almost identical, blurring any previous empirical, analytical, or normative distinctions. In their Greco-Roman synthesis dictatorship is re-described as `temporary tyranny by consent' and the tyrant as a `permanent dictator.' Dictatorship, a venerated republican magistracy, the ultimate guardian of the Roman constitution, is for the first time radically reinterpreted and explicitly questioned. It meets its first critics. (shrink)