(Φυλλίδας), a Theban. was secretary to the polemarchs who held office under Spartan protection, after the seizure of the Cadmeeia by Phoebidas, in B. C. 382. He was, however, a secret enemy of the new government, and appears to have made interest for the office which he occupied with the view of aiding the cause of freedom. Having been sent by his masters on some business to Athens, where the exiles had taken refuge, he arranged with them the particulars of their intended enterprise against the tyrants, and afterwards most effectually aided its execution in B. C. 379. Thus, having especially ingratiated himself with Archias and Philippus, of whose pleasures he pretended to be the ready minister, he introduced, in the disguise of women, the conspirators who despatched them; he gained admittance, according to Xenophon, for Pelopidas and his two companions to the house of LEONTIADES; and, before what had happened could be publicly known, he effected, with two others, his entrance into the prison, under pretence of an order from the polemarchs, and, having slain the jailor, released those who were confined there as enemies to the government. (Xen. Hell. 5.4. §§ 2-8; Plut. Pel. 7, &c., de Gen. Soc. 4, 24, 26, 29, 32; Diod. 15.25.)