The Siege of Cyzicus was a major military engagement occurring in 73 BC during the Third Mithridatic War. The conflict pitted the forces of Mithridates VI of Pontus against the city of Cyzicus in Mysia, which was supported by the Roman Republic.
The operation was characterized by a complex dynamic of both a siege and a counter-siege, as Roman forces under Lucius Licinius Lucullus arrived to relieve the city. The engagement concluded in a decisive Roman victory, which significantly hampered the offensive capabilities of the Pontic army and shifted the momentum of the war in favor of Rome.