Marcus Antonius Primus (30/35 – after 81 AD) was a senator and general of the Roman Empire.
Primus was born at Tolosa (Toulouse) in Gaul. During the reign of Nero, he was resident in Rome and a member of the Senate, from which he was expelled for conspiring to forge a will with Valerius Fabianus, and was banished from the city. He was subsequently reinstated by Galba, and placed in command of the Legio VII Galbiana in Pannonia.
During the civil war, Primus was one of Vespasian's strongest supporters. Advancing into Italy, he gained a decisive victory over the Vitellians at Bedriacum in October 69, and on the same day stormed and set fire to Cremona. He then crossed the Apennines, and made his way to Rome, into which he forced an entrance after considerable opposition. Vitellius was seized and put to death. For a few days, Primus was virtually ruler of Rome, and the Senate bestowed upon him the rank and insignia of a consul, but on the arrival of Licinius Mucianus, he left Rome.
Primus must have been alive during the reign of Domitian, since four epigrams of Martial are addressed to him. Tacitus describes him as brave in action, ready of speech, clever at bringing others into odium, powerful in times of civil war and rebellion, greedy, extravagant, in peace a bad citizen, in war an ally not to be despised.