Who is the lady in painting Madame X?

Madame X or Portrait of Madame X is the informal title of a portrait painting by John Singer Sargentof a young socialite named Virginie Amélie Avegno Gautreau, wife of Pierre Gautreau. The model was an American expatriate who married a French banker, and became notorious in Parisian high society for her beauty and rumored infidelities. She wore lavender powder and prided herself on her appearance.