(Ἀριστόμαχος).
1. Tyrant of Argos, in the reign and under the patronage of Antigonus Gonatas. He kept the citizens of Argos in a defenceless condition, but a conspiracy was formed against him, and arms were secretly introduced into the town by a contrivance of Aratus, who wished to gain Argos for the Achaean league. The plot was discovered, and the persons concerned in it took to flight. But Aristomachus was soon after assassinated by slaves, and was succeeded by Aristippus II. (Plut. Arat. 25.)