(Ὀνήσιλος), of Salamis in Cyprus, the son of Chersis, grandson of Siromus, and greatgrandson of Evelthon. He had frequently urged his brother Gorgus, who was king of Salamis in Cyprus, to desert from the Persians; but as he was unable to persuade him to do so, he finally drove him from the city, and set up the standard of revolt with the Ionians, in B. C. 499. Gorgus fled to the Persians; Onesilus became king of Salamis, and persuaded all the other cities in Cyprus, with the exception of Amathus, to renounce their allegiance to the Persians. Thereupon Onesilus laid siege to Amathus; and as Dareitis sent a large force to its relief under the command of Artybios, Onesilis begged aid of the Ioniams. They readily complied with his request; and in the following year, B. C. 498, two battles were fought between the contending parties, one by sea, in which the lonians defeated the Phoenician fleet, and the other by land, in which the Cyprians were beaten by the Persians. Onesilus fell in the battle; his head was cut off by the inhabitants of Anmathus, and hung over their city-gates. At a later period, however, an oracle commanded them to take down his head and bury it, and also to offer sacrifices to him as a hero. (Hdt. 5.104, 108_110.) [GORGUS, No. 2.]