Battle of Pydna, (June 22, 168 bce), decisive military engagement in the Roman victory over Macedonia in the Third Macedonian War. The Roman general Lucius Aemilius Paullus, by means of adroit tactical maneuvering, enticed the Macedonian king Perseus from his impregnable position on the Elpeus (Mavrólongos) River to occupy a weaker position in the plain south of Pydna (now Kítros, Greece; the actual site was probably near Kateríni).

The battle pitted the Macedonian phalanx against the Roman legion, with the latter emerging as the more-versatile fighting formation. The Macedonians’ tight ranks were left in a state of disorder after crossing broken ground, a vulnerability that was exploited by the Roman legionaries, whose short swords were more effective in close combat than were the Macedonian pikes. Perseus’s left wing of Thracians and light troops was defeated by the Roman allies. Macedonian losses were great; of the estimated 40,000 engaged, some 25,000 were killed and more than 10,000 were made prisoner. Perseus fled, allowing the Romans to end the Macedonian monarchy and divide Macedonia into four republics.