Château-Landon is a commune in the Seine-et-Marne department in the Île-de-France region in north-central France. The commune contains the Souppes-sur-Loing quarry, where the bright white travertine stones for the construction of the Sacré-Cœur, Paris, were sourced. Formerly the seat of the canton of Château-Landon, it has been part of the canton of Nemours since 2015.