Lycomedes, a Mantinean, according to Xenophon and Pausanias, wealthy, high-born, and ambitious. Diodorus calls him in one passage a Tegean; but there can be no question (though Wesseling would raise one) of the identity of this Lycomedes with the Arcadian general whom he elsewhere speaks of as a Mantinean. (Xen. Hell. vii. 1. § 23; Paus. viii. 27; Diod. xv. 59, 62; Wess. ad Diod. xv. 59; Schneider, ad Xen. Hell. vi. 5. § 3.) We first hear of him as one of the chief founders of Megalopolis in 370 BC , and Diodorus (xv. 59.) tells us that he was the author of the plan, though the words of Pausanias (viii. 27, ix. 14.) would seem to ascribe the origination of it to Epaminondas. (Comp. Arist. Pol. ii. 2, ed. Bekk.; Xen. Hell. vi. 5. § 6, &c.) In 369 BC Lycomedes was general of the Arcadians and defeated, near Orchomenus, the forces of the Lacedaemonians under Polytropus. (Xen. Hell. vi. 5. § 14; Diod. xv. 62.)

In the following year we find symptoms of a rising jealousy towards Thebes on the part of the Arcadians, owing in great measure to the suggestions and exhortations of Lycomedes, who reminded his countrymen of their ancient descent as the children of the soil, of their numbers, their high military qualifications, and of the fact that their support was quite as important to Thebes as it had been to Lacedaemon; and it is possible that the spirit thus roused and fostered in Arcadia may have shortened the stay of Epaminondas in the Peloponnesus on this his second invasion of it. The vigour exhibited in consequence by the Arcadians under Lycomedes and the successes they met with are mentioned by Xenophon and Diodorus, the latter of whom however places these events a year too soon. Thus it was in 369 BC, according to him, that Lycomedes marched against Pellene in Laconia, and, having taken it, made slaves of the inhabitants and ravaged the country. (Xen. Hell. ii. 1. §§ 23, &c.; Diod. xv. 67; Wess. ad loc.) The same spirit of independence was again manifested by Lycomedes in 367 BC, at the congress held at Thebes after the return of the Greek envoys from Susa; for when the rescript of Artaxerxes II. (in every way favourable to Thebes) had been read, and the Thebans required the deputies of the other states to swear compliance with it, Lycomedes declared that the congress ought not to have been assembled at Thebes at all, but wherever the war was. To this the Thebans answered angrily that he was introducing discord to the destruction of the alliance, and Lycomedes then withdrew from the congress with his colleagues. (Xen. Hell. vii. 1. § 39.)

In 366 BC, the loss of Oropus having exasperated the Athenians against their allies, who had with-held their aid when it was most needed, Lycomedes took advantage of the feeling to propose an alliance between Athens and Arcadia. The proposal was at first unfavourably received by the Athenians, as involving a breach of their connection with Sparta; but they afterwards consented to it on the ground that it was as much for the advantage of Lacedaemon as of Athens that Arcadia should be independent of Thebes. Lycomedes, on his return by sea from Athens, desired to be put on shore at a certain portion of the Peloponnesian coast, where there happened to be collected a number of Arcadian exiles; and by these he was murdered. (Xen. Hell. vii. 4. §§ 2, 3.)