Macrobius Ambrosius Theodosius, (fl. c. AD 400), was a Roman provincial who lived during the early fifth century. He survives only in his writings. His commentaris on Cicero's Dream of Scipio would be a key source for Neoplatonism in the Latin West, and included some foundational discussion of the nature of the world and the cosmos. He also produced his Saturnalia, a collection of Roman religious and antiquarian lore; and a lost linguistic work, De differentiis et societatibus graeci latinique verbi ("On the Differences and Similarities of the Greek and Latin Verb"), which is now lost.

Virtually nothing is known of Macrobius. In his Saturnalia he said of himself that he was 'born under a foreign sky' but of which sky, scholarship is uncertain; he may have been Greek, but his facility with Latin has led to speculation that this was his first language and that he hailed from a Latin-speaking part of the Empire. Nothing is certain.