This article publishes a new text by Giannozzo Manetti and places it into the political, diplomatic, and biographical context from which it emerged.  Manetti’s “Panegyric to King Alfonso” was written for the occasion of the Holy Roman Emperor Frederick III’s visit to Naples in the spring of 1452.  This article and the accompanying first edition of Manetti’s treatise add new insights into the events of mid-Quattrocento Italy that led to Manetti’s voluntary exile from Florence, in addition to a new chapter in the narrative of patrician resistance to the consolidation of political power in Florence under Cosimo de’ Medici and his allies.