Magistra vitae is a Latin expression, used by Cicero in his De Oratore as a personification of history, means "life's teacher". Often paraphrased as Historia est Magistra Vitae, it conveys the idea that the study of the past should serve as a lesson to the future, and was an important pillar of classical, medieval and Renaissance historiography.

The complete phrase, with English translation, is:

Historia vero testis temporum, lux veritatis, vita memoriae, magistra vitae, nuntia vetustatis, qua voce alia nisi oratoris immortalitati commendatur?

By what other voice, too, than that of the orator, is history, the witness of time, the light of truth, the life of memory, the directress of life, the herald of antiquity, committed to immortality?

Cicero, De Oratore, II, 36.^[1][2]

• Cicero, Marcus Tullius (1860). On oratory and orators. Translated by Watson, J. S. New York: Harper & Brothers.
• Cicero, Marcus Tullius (1862). De oratore. Leipzig: B.G. Teubner.