Legio quarta Macedonica ("Macedonian Fourth Legion"), was a legion of the Imperial Roman army founded in 48 BC by Gaius Julius Caesar (dictator of Rome 49-44 BC) with Italian legionaries. The legion was disbanded in AD 70 by Emperor Vespasian. The legion symbols were a bull (as with all of Caesar's legions) and a capricorn.
In 48 BC, the Roman Republic was decaying rapidly. Caesar had crossed the Rubicon River in the year before, starting a civil war. Pompey, Cato the younger and the rest of the conservative faction of the senate had fled to Greece. Caesar was preparing to follow in pursuit and, among other preparations, levied Legio V. The first battles of the legion were Dyrrhachium and Pharsalus, where Caesar defeated Pompey. After this, the legion was stationed in the province of Macedonia, attaining thus its cognomen.
IV Macedonica sided always with Julius Caesar's adopted son, Octavian, first against Caesar's murderers in the Battle of Philippi in 42 BC, then against Mark Antony in the naval Battle of Actium in 31 BC.
Octavian, now Augustus, sent the legion to Hispania Tarraconensis in 30 BC, to take part in the Cantabrian Wars. In 25 BC, they served as the decisive force in the Battle of Vellica under the personal command of Augustus. After Augustus' victory in 13 BC, the legion remained in the province, but its effectives were spread through the Iberian Peninsula.