Eugène Emmanuel Viollet-le-Duc was a French architect and author who restored many prominent medieval landmarks in France, including those which had been damaged or abandoned during the French Revolution. His major restoration projects included Notre-Dame de Paris, the Basilica of Saint Denis, Mont Saint-Michel, Sainte-Chapelle, and the medieval walls of the city of Carcassonne.

His later writings on the relationship between form and function in architecture had a notable influence on a new generation of architects, including Victor Horta, Hector Guimard, Antoni Gaudí, Hendrik Petrus Berlage, Louis Sullivan and Frank Lloyd Wright.