When the French invaded Italy in 1494, they were shocked by the frank sexuality expressed in Italian cities. By 1600, the French were widely considered to be the most highly sexualized nation in Christendom. What caused this transformation? This book examines how, as Renaissance textual practices and new forms of knowledge rippled outward from Italy, the sexual landscape and French notions of masculinity, sexual agency, and procreation were fundamentally changed. Exploring the use of astrology, the infusion of Neoplatonism, the critique of Petrarchan love poetry, and the monarchy's sexual reputation, the book reveals that the French encountered conflicting ideas from abroad and from antiquity about the meanings and implications of sexual behavior. Intensely interested in cultural self-definition, humanists, poets, and political figures all contributed to the rapid alteration of sexual ideas to suit French cultural needs. The result was the vibrant sexual reputation that marks French culture to this day.