Le secret du Chevalier d'Éon (1959)

Le secret du Chevalier d'Éon is a 1959 Italian film. It stars actor Gabriele Ferzetti. It is loosely based on the life of Chevalier d'Éon, although it portrays her as a woman masquerading as a man, rather than a transgender woman (biologically male but presenting as a woman, at least in the latter part of her life) as was the true situation.

More at Wikipedia.