(Ἰσμενίας), a Theban, of the party adverse to Rome and friendly to Macedonia. When he was chosen Boeotarch, a considerable number of the opposite faction were driven into exile, and condemned to death by him in their absence. These men met, at Larissa in Thessaly, the Roman commissioners, who were sent into Greece in B. C. 171, preparatory to the war with Perseus; and on being upbraided with the alliance which Boeotia had made with the Macedonians, they threw the whole blame on Ismenias. Shortly after they appeared before the commissioners at Chalcis; and here Ismenias also presented himself, and proposed that the Boeotian nation should collectively submit to Rome. This proposal, however, did not at all suit Q. Marcius and his colleagues, whose object was to divide the Boeotian towns, and dissolve their confederacy. They therefore treated Ismenias with great contumely; and his enemies being thereby emboldened to attack him, he narrowly escaped death by taking refuge at the Roman tribunal. Meanwhile, the Roman party entirely prevailed at Thebes, and sent an embassy to the Romans at Chalcis, to surrender their city, and to recal the exiles. Ismenias was thrown into prison, and, after some time, was put to death, or (as we may perhaps understand the words of Polybius) committed suicide. (Liv. 42.38, 43, 44; Plb. 27.1, 2.)