Between 1559 and 1589, Catherine de Médicis developed an acute understanding of the role of the arts in expressing power and political influence. This article argues that the celebrations organized for the meeting of the French and Spanish courts at Bayonne in 1565 demonstrate Catherine’s keen understanding of the power of visual culture, and skill at manipulating images in the service of diplomacy. As de facto ruler of France, she reinterpreted popular forms of entertainments and developed new imagery that promoted herself and her son, King Charles IX, as well as asserted her own political legitimacy and that of the ruling Valois dynasty. The fêtes at Bayonne were essential in defining Catherine’s role as one of Europe’s most influential art patrons. The new forms of entertainments devised on the occasion, and their sophisticated visual propaganda, would become characteristic of both a true French Renaissance and a nascent baroque culture.