Timarchus: name of pretender who was briefly king in the eastern part of the Seleucid Empire (r.163-160).
- Father: Heraclides
- Page at the court of king Antiochus IV Epiphanes.
- Ambassador of Antiochus IV Epiphanes to Rome.
- Strategos responsible for the eastern part of the Seleucid Empire; this means he had to defend it against the Parthians. His brother Heraclides acts as treasurer.
- Founder of the Bouleuterion of Miletus.
- November/December 164: death of Antiochus IV, who is succeeded by Antiochus V Eupator; Lysias acts as regent; in Media, revolt of Timarchus. He is supported by king Artaxias of Armenia.
- After 29 October 162: Antiochus is overthrown and killed by Demetrius I Soter; Timarchus accepts the title of "great king" (like king Eucratides of Bactria, who had accepted this title a couple of years earlier).
- Timarchus is in control of Babylonia.
- 160: Demetrius overthrows Timarchus and accepts the title Soter, "savior", from the grateful Babylonians.
- The extent of the realm of Timarchus is contested. Was he governor of all territories east of the Euphrates or Tigris? In the first case, he was responsible for Babylonia too; in the second case, he must have waged war to conquer it.