(Ἐτεόνικος), a Lacedaemonian, who in B. C. 412 was lieutenant under the admiral Astyochus, and assisted him in his unsuccessful operations against Lesbos. (Thuc. 8.23.) He was afterwards harmost in Thasos, but in 410, together with the Lacedaemonian party, was expelled by the Thasians. (Xen. Hell. 1.1.32.) In 406 we find him serving under Callicratidas, who left him to blockade Conon in Mytilene, while he himself went to meet the Athenian reinforcements. After the battle of Arginusae, by means of a stratagem, Eteonicus succeeded in drawing off the land forces to Methymna, while he directed the naval forces to make with all speed for Chios, where he found means of rejoining them not long afterwards. In the course of his stay here, he, with considerable energy and promptitude, defeated a plot forced by some of the troops under his command to seize Chios. (Xen. Hell. 1.6.26, 36, &c., 2.1.1, &c.) It is probably this Eteonicus whom we find mentioned in the Anabasis (7.1.12) apparently serving as an officer under Anaxibius at Byzantium. (B. C. 400.) Eleven years afterwards (389), he is mentioned as being stationed as harmost in Aegina. (Xen. Hell. v. 1.1.)