Chiliarch: official at the royal court of Achaemenid Persia.
Chiliarchos means "leader of a thousand men" and is the Greek way to describe an official the Achaemenid court who was in charge of the daily, official affairs of the king. The Persian name may have been hazarapatiš. Although chiliarchos has often been translated as vizier, the precise nature of this office are not clear. The only thing that is certain is that the chiliarch decided who had access to the king. Examples are Bagoas, the chiliarch of Artaxerxes IV, and Nabarzanes, the right-hand man of Darius III.
Alexander the Great appointed Hephaestion and, later, Perdiccas as chiliarch. After Alexander's death, Cassander is mentioned as chiliarchs. The office also existed in Hellenistic courts.