On 17 September 1839, Richard Wagner arrived in Paris. Although scholars agree that the composer learned a great deal about aesthetics during his first sojourn in the city, what has not been known is exactly what he learned and from whom. This Element explores the striking similarities between Wagner's early aesthetic writings and François Delsarte's 'Cours d'esthétique appliquée', a theoretical and practical training course for artists which Delsarte began teaching in Paris in May 1839. This Element also details the rise of Delsarte as a celebrated teacher of aesthetics and interpreter of Gluck's repertoire during the same years that Wagner lived in the city. By comparing historical timelines, published documents, and manuscript sources and by analysing Wagner's treatises, Das Kunstwerk der Zukunft and Oper und Drama, and the essay 'Über Schauspieler und Sänger', the author shows that Delsarte's course is the most likely source of Wagner's aesthetic transformation in Paris.