A provincial governor of the Achaemenids, as first established by Darius I (the Great) who divided his empire up into twenty satrapies. Although the satraps nominally owed allegiance to the king, the considerable power and autonomy vested in them fostered disloyalty and there were frequent uprisings, the most notable being that of 366–358 bc against Artaxerxes II. Alexander the Great retained the system after his conquest, as did the Parthians, but under the Sassanian empire the term “satrap” designated a less important figure.