(Κοιρατάδας), a Theban, commanded some Boeotian forces under Clearchus, the Spartan harmost at Byzantium, when that place was besieged by the Athenians in B. C. 408. When Clearchus crossed over to Asia to obtain money from Pharnabazus, and to collect forces, he left the command of the garrison to Helixus, a Megarian, and Coeratadas, who were soon after compelled to surrender themselves as prisoners when certain parties within the town had opened the gates to Alcibiades. [CLEARCHUS.] They were sent to Athens, but during the disembarkation at the Peiraeeus, Coeratadas contrived to escape in the crowd, and made his way in safety to Deceleia. (Xen. Hell. 1.3. §§ 15-22; Diod. 13.67; Plut. Alc. 31.) In B. C. 400, when the Cyrean Greeks had arrived at Byzantium, Coeratadas, who was going about in search of employment as a general, prevailed on them to choose him as their commander, promising to lead them into Thrace on an expedition of much profit, and to supply them plentifully with provisions. It was however almost immediately discovered that he had no means of supporting them for even a single day, and he was obliged accordingly to relinquish his command. (Xen. Anab. 7.1. §§ 33-41.)