This article revisits the anonymous Panegyricus Latinus 12(9) in praise of Constantine’s victory against Maxentius at the Battle of the Milvian Bridge. Delivered in 313 ce, a year after the decisive battle during which Maxentius was drowned in the Tiber while trying to flee, the speech is known for its use of Virgilian motifs. I argue that the author draws systematically on the discussion of clemency and retribution which ancient commentators (Serv. 12.940) and modern scholars alike have long suspected to be the focus of the second half of the Aeneid. The author of 12(9) draws on a specific reading of the Aeneid according to which Constantine, who is compared to Aeneas and Augustus, is justified for his excessive use of force, while Maxentius, who is compared to several tyrannical figures in the Aeneid, deserved his miserable death. Eusebius, who systematically engaged with the tradition of the Latin panegyrics, further developed the motifs introduced in 12(9) by casting Constantine as a divinely sent freedom fighter against tyrants (Maxentius, but also Licinius and Maximinus). Thus, the author’s display of his rhetorical training contributes creatively to Constantine’s political agenda and inspires Eusebius to Christianize Virgil.