ETHNARCH, (formed of ἐθνος, "nation," and ἄρχω, "command"), a governor or ruler of a nation.

There are some medals of Herod I. surnamed the Great, on one side whereof is found Ἑρῴδου, and on the other Ἐθνάρχου, q. d. Herod the Ethnarch. After the battle of Philippi, we read that Antony, passing over into Syria, constituted Herod and Phasael his brother tetrarchs, and in that quality committed to them the administration of the affairs of Judea, (Jof. Ant. lib. xiv. cap. 23.) Herod therefore had the government of the province before ever the Parthians entered Syria, or before Antigonus's invasion, which did not happen till six or seven years after Herod was commander in Galilee, (Jof. lib. xiv. cap. 24, 25.) Consequently, Herod was then truly ethnarch, for he can be no otherwise denominated; so that it must have been in that space of time that the medals were struck, which only give him this title: which medals are a confirmation of what we read in history of the government which that prince was intrusted with before he was raised to the royalty.

Josephus gives Herod the appellation of tetrarch in lieu of that of ethnarch; but the two terms come so near to each other, that it is easy to confound them together.

Though Herod the Great left by will to Archelaus all Judea, Samaria, and Idumea, yet Josephus tells us he was then only called ethnarch.