Marguerite Louise d'Orléans (28 July 1645 – 17 September 1721) was Grand Duchess of Tuscany, as the wife of Grand Duke Cosimo III de' Medici. Deprived of her lover, Charles V of Lorraine, Marguerite Louise despised her husband and his family, whom she often quarrelled with and falsely suspected of attempting to poison her. Marguerite Louise reconciled with the Medici on more than one occasion, however, only to promptly resume hostilities.
In June 1675, Marguerite Louise was allowed to return to France to live in a convent in Paris. She was a daughter of Gaston de France, Duke of Orléans. Although the contract, banned her from leaving the convent, Marguerite Louise often went to her cousin Louis XIV's court at Versailles. She was at the centre of many scandals at the convent, including an attempt to burn it down, which greatly irritated her husband, who, despite the separation, took great interest in Marguerite Louise's life. While still technically married, Marguerite Louise had several affairs.