The Third Macedonian War (171 BC - 168 BC) was a war fought between Rome and King Perseus of Macedon. In 179 BC King Phillip V of Macedonia died and his talented and ambitious son, Perseus, took his throne. Perseus married Laodike, daughter of King Seleucus IV Keraunos of Asia, increased the size of his army and made alliance treaties with Epirus and several tribes of Illiria and Thrace. He renewed former connections with some Greek city-states (poleis). The king announced that he could carry out reforms in Greece and restore its previous strength and prosperity.

The Romans began to worry that Perseus would destroy Roman political control in Greece and restore former Macedonian sovereignity over Greek states. King Eumenes II of Pergamon, who hated Macedonia, accused Perseus of trying to violate laws of other states and conditions of peace between Macedonia and Rome. The Romans were afraid of the fall of the balance of power and declared a new war with Macedonia. Perseus won the first struggle: the battle of Larissa, where he faced the army of Publius Licinius Crassus. The king offered a peace treaty to the Romans, which was refused. For a long time the Romans had problems with discipline in their army, and Roman commanders couldn't find a way to successfully invade the territory of Macedonia.

Meanwhile, Perseus defeated another Roman army in Illiria. The Macedonian king tried to win Eumenes of Pergamon and king Antiochus III the Great of Asia over to his side but he failed. In 169 BC consul Qiuntus Marcius Phillipus crossed the Olimp mountains and entered Macedonia. His army was at first too exhausted to fight following the crossing, though. Finally, Perseus was defeated by the legions of the Roman consul Lucius Aemlius Paullus at the Battle of Pydna in 168 BC. Perseus was deposed and with his dignitaries taken to Rome. Macedon was divided into four Roman client republics. The inhabitants of those republics had to pay a tax to Rome, although it was not large. Ecconomical and political contacts between Macedonian and Greek states were reduced. That was the end of hellenistic Macedonia and the monarchy of Antygonid dynasty.