Which emperor appears in the sphere of Mercury in Paradiso VI?

Justinian I appears in the sphere of Mercury in Paradiso VI. Dante places Mercury second among the celestial spheres, associating it with souls who performed good works but were influenced by ambition and the desire for earthly fame.

Justinian, the Byzantine emperor who ruled from 527 to 565, appears as a luminous spirit and recounts the history of the Roman eagle, the symbol of imperial authority. His speech traces Rome’s imperial story from Aeneas through the Roman Republic and Empire to the time of Charlemagne. He also explains the role of the Roman Empire in Dante’s providential view of history and describes his own conversion to orthodox Christianity under Pope Agapetus.

The canto then turns to the Crucifixion and the later destruction of Jerusalem, linking Roman power with salvation history. Dante’s Justinian is therefore not merely a historical cameo: he is a spokesman for the relationship between empire, justice, and divine providence. Frederick II and Charlemagne are important emperors in medieval history, while Constantine appears elsewhere in Paradiso, but Justinian is the emperor Dante meets in Mercury.