On the night of 6 January 1537 Lorenzo di Pierfrancesco de' Medici killed his cousin, the first Duke of Florence, Alessandro de' Medici. In an Apologia, written around three years after the assassination, Lorenzo claimed that he had killed Alessandro in order to restore Florence to republican liberty. Historians have interpreted this text as a self-justificatory and self-aggrandizing piece. This article argues that the Apologia is better understood as an example of revenge humanism, and that its purpose was not to justify the assassination of Alessandro, but to defend Lorenzo's own name. The narrative of the Apologia presented Lorenzo as the defender of Florence's republican and civic traditions, but it did so within the culture and etiquette of sixteenth-century court society. Lorenzo was fighting a verbal duel with the contemporary critics who accused him of lacking honor, courage, and integrity.