or HI'DRIEUS (Ἰδριεύς, Diod. ; Ἱδριεύς, Strab. Arr.), king or dynast of Caria. He was the second son of Hecatomnus, and succeeded to the throne on the death of Artemisia, the widow of his brother Maussolus, in B. C. 351. Shortly after his accession he was required by the Persian king, Artaxerxes Ochus, to fit out an armament for the reduction of Cyprus, a request with which he readily complied; and having equipped a fleet of 40 triremes, and assembled an army of 8000 mercenary troops, despatched them against Cyprus, under the command of Evagoras and the Athenian general Phocion. This is the only event of his reign which is recorded to us; but we may infer, from an expression of Isocrates, in B. C. 346 (Philipp. p. 102e), that the friendly relations between him and the Persian king did not long continue : they appear to have come even to an open rupture. But the hostility of Persia did not interfere with his prosperity, for he is spoken of by Isocrates in the same passage as one of the most wealthy and powerful of the princes of Asia; and Demosthenes tells us (de Pace, p. 63) that he had added to his hereditary dominions the important islands of Chios, Cos, and Rhodes. He died of disease in B. C. 344, after a reign of seven years, leaving the sovereign power, by his will, to his sister Ada, to whom, according to the eastern custom, he had been married. (Diod. 16.42, 45, 69; Strab. xiv. p.656; Arr. Anab. 1.23.8_10.)