Marguerite Leferon (née Galart; d. after 1679), was an accused in the famous Affair of the Poisons.
When De Prade proved to be a fortune hunter she decided to murder him as well, which was prevented by his escape.
The case against Marguerite Leferon and Françoise de Dreux, 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.
The light sentences imposed on them, despite their guilt, was considered damaging to the legitimacy of the court.
One example was that of Madame Philbert, who in 1673 murdered her carpenter husband Brunet by poison of Marie Bosse in order to marry her lover, Philippe Rebille Philbert: her crime was identical to that of Leferon, but she was sentenced to hang after having her right hand cut off.