(Κλείταρχος), tyrant of Eretria in Euboea. After Plutarchus had been expelled from the tyranny of Eretria by Phocion, B. C. 350, popular government was at first established ; but strong party struggles ensued, in which the adherents of Athens were at length overpowered by those of Macedonia, and Philip then sent Hipponicus, one of his generals, to destroy the walls of Porthmus, the harbour of Eretria, and to set up Hipparchus, Automedon, and Cleitarchus as tyrants. (Plut. Phoc. 13; Dem. (de Cor. § 86, Philipp. 3. §§ 68, 69.) This was subsequent to the peace between Athens and Philip in B. C. 346, since Demosthenes adduces it as one of the proofs of a breach of the peace on the part of Macedon. (Philipp. 3.23.) The tyrants, however, were not suffered to retain their power quietly, for Demosthenes (Philip. 3.69) mentions two armaments sent by Philip for their support, at different times, under Eurylochus and Parmenion respectively. Soon after, we find Cleitarchus in sole possession of the government ; but he does not seem to have been at open hostility with Athens, though he held Eretria for Philip, for we hear of the Athenians sending ambassadors to request his consent to the arrangement for uniting Euboea under one federative government, having its congress at Chalcis, to which Athens was also to transfer the annual contributions from Oreus and Eretria. Aeschines says, that a talent from Cleitarchus was part of the bribe which he alleges that Demosthenes received for procuring the decree in question. Cleitarchus appears therefore to have come into the above project of Demosthenes and Callias, to whom he would naturally be opposed; but he thought it perhaps a point gained if he could get rid of the remnant of Atheian influence in Eretria. For the possible motives of Demosthenes, see p. 568a. The plan, however, seems to have fallen to the ground, and Demosthenes in B. C. 341 carried a decree for an expedition to Euboea with the view of putting down the Macedonian interest in the island. On this, Cleitarchus and Philistides, the tyrant of Oreus, sent ambassadors to Athens to prevent, if possible, the threatened invasion; and Aeschines, at whose house the envoys were entertained, appears to have supported their cause in the assembly. But the decree was carried into effect, and the command of the armament was given to Phocion, by whom Cleitarchus and Philistides were expelled from their respective cities. (Aesch. c. Ctes. §§ 85-103; Dem. de Cor. p. 252, &c. ; Diod. 16.74; Plut. Demi. 17.)