Élisabeth Marguerite d'Orléans, known as Isabelle d'Orléans, was the Duchess of Alençon and, during her husband's lifetime, Duchess of Angoulême. She was a daughter of Gaston d'Orléans and a first cousin of Louis XIV of France. She has no descendants today. She was suo jure Duchess of Alençon and Angoulême.

Monsieur Gaston, Duke of Orléans, was the third son of King Henry IV of France and his second wife, Marie de' Medici. As a son of the king, he was born a Fils de France. He later acquired the title Duke of Orléans, by which he was generally known during his adulthood. As the eldest surviving brother of King Louis XIII, he was known at court by the traditional honorific Monsieur.