Telesarchus (Τελέσαρχος), a Syro-Macedonian officer, who commanded a force of 500 men sent by Antiochus I. to assist the Greeks in the defence of Thermopylae against the Gauls under Brennus, 279 BC. On that occasion he displayed the utmost zeal and courage, and rendered important services to the cause of the confederates, but was at length slain while valiantly defending a side pass over Mount Oeta, by which the Gauls sought to force their passage. (Paus. x. 20. § 5, 22. § 1.)