Le Fils naturel (English: The Natural Son) is a 1757 play by Denis Diderot. This play tells the story of Dorval, a young man of unknown parentage, who is welcomed into the family of Clairville and his widow sister Constance. Rosalie, Clairville's fiancé, also lives there. Dorval and Rosalie fall in love, and Dorval struggles with his love for Rosalie and his respect for Clairville.