Against Timarchus (Greek: Κατὰ Τιμάρχου) was a speech by Aeschines accusing Timarchus of being unfit to involve himself in public life. The case was brought about in 346/5, in response to Timarchus, along with Demosthenes, bringing a suit against Aeschines, accusing him of misconduct as an ambassador to Philip II of Macedon. The speech provides evidence of a number of actions which, according to Aeschines, would cause a citizen to lose the right of addressing the Assembly. Aeschines accuses Timarchus of two of these forbidden acts: prostituting himself, and wasting his inheritance. Along with the accusations of prostitution and squandering his inheritance for which Timarchus was on trial, the speech contains charges of "bribery, sycophancy, the buying of office, embezzlment, and perjury".
Modern scholars have criticised the lack of evidence that Aeschines put forward in Against Timarchus, for instance by pointing out that he has no evidence that any of Timarchus' lovers ever paid him. Indeed, Hubbard observes that he does not even manage to produce a single witness who will testify that Timarchus had any sexual relationship with the men in question at all. Despite this, he won the case and Timarchus was punished by disenfranchisement.
Timarchus or Timarch was a usurper in the Seleucid empire between 163–160 BC.
A Greek nobleman, possibly from Miletus in Asia Minor, Timarchus was a friend of the Seleucid prince Antiochus IV Epiphanes during his time as a hostage to the Roman Republic. He was appointed satrap of Media in western Iran when Antiochus IV Epiphanes became king in 175 BC, and his brother Heracleides became minister of the royal finances. The Persian part of the empire was threatened by the Parthian kingdom, and Timarchus probably spent much of his time reinforcing the defences. The Seleucid realms probably extended as far as the area of Teheran during this time.
In the turmoil following the death of Antiochus IV during a Persian campaign in 163 BC, Timarchus became the more or less independent ruler of Media, opposing the general Lysias who acted as steward for the infant king Antiochus V Eupator, son of Antiochus IV.
In 162 BC Demetrius I, the proper heir to the Seleucid throne, became king, killing Lysias as well as the young Antiochus V. This may well have been the provocation that caused Timarchus to take the final step to independence and declare himself king.