Françoise de Dreux (d. after 1681) was a French noble, an accused in the famous Affair of the Poisons.
Françoise de Dreux was married to a member of the Paris Parlement and cousin of two judges in the Poison Affair.
She left the country to avoid arrest, and upon the appeal from both her husband and her lover, she was spared any punishment for her crimes except exile from the capital.
The case against Françoise de Dreux and Marguerite Leféron, as well as that of Marguerite de Poulaillon, attracted attention as they were the first clients, and the first members of the upper classes to be implicated in the affair, and the light sentences toward them, despite their guilt, was considered damaging for the legitimacy of the court; they were obviously a proof of class discrimination, as others accused of the same crime in the case, but belonging to a different social class, were sentenced to be executed.
One example was that of Madame Philbert, who in 1673 murdered her carpenter husband Brunet by poison from Marie Bosse in order to marry her lover, musician Philippe Rebille Philbert: her crime was identical to that of Leféron, but she was sentenced to hang after having her right hand cut off.