Antony's Parthian War was a military campaign by Mark Antony, the eastern triumvir of the Roman Republic, against the Parthian Empire under Phraates IV.
Julius Caesar had planned an invasion of Parthia but was assassinated before he could implement it. In 40 BC, the Parthians were joined by Pompeian forces and briefly captured much of the Roman East, but a force sent by Antony defeated them and reversed their gains.
Allying with several kingdoms, including Armenia, Antony began a campaign against Parthia with a massive force in 36 BC. The Euphrates front was found to be strong and so Antony chose the route via Armenia. Upon entering Atropatene, the Roman baggage train and siege engines, which had taken a different route, were destroyed by a Parthian cavalry force. Antony still besieged the Atropatene capital but was unsuccessful.
The arduous journey of retreat to Armenia and then Syria further inflicted heavy losses on his force. Roman sources blame the Armenian king for the heavy defeat, but modern sources note Antony's poor management and planning. Antony later invaded and pillaged Armenia and executed its king.