Virgil
Dante made Virgil his guide in Hell and the greater part of Purgatory in The Divine Comedy. Dante also mentions Virgil in De vulgari eloquentia, along with Ovid, Lucan and Statius, as one of the four regulati poetae (ii, vi, 7).

Q: In which of Dante's works was Virgil a guide through Hell and Purgatory?
Divine Comedy