Françoise-Marguerite was born in Paris in 1646, she was the daughter of Henri de Sévigné and Marie de Rabutin Chantal, Marquise de Sévigné.
Around the age of 16, Françoise-Marguerite danced alongside King Louis XIV in court ballets. For her cousin Bussy Rabutin, she was "the prettiest girl in France".
On January 29, 1669, she married François de Castellane-Adhémar, Count of Grignan. Settled in Provence with her husband, amidst separations and reunions, numerous letters were exchanged between Françoise-Marguerite, Countess of Grignan, and her mother, the Marquise de Sévigné.
She had three children, including Pauline, the future Marquise de Simiane, who played an important role in disseminating her grandmother's correspondence. The Countess of Grignan died in Mazargues (Marseille) on August 5, 1705, at the age of 59.
