Maria Teresa Felicitas d'Este (October 6, 1726 – April 30, 1754) was born a princess of Modena and was by marriage the Duchess of Penthièvre. She was the mother-in-law of Philippe Égalité and thus grandmother to the future Louis-Philippe of France.

Born in Emilia-Romagna in Modena, she was the daughter of Francesco III, Duke of Modena and his wife, the French princess Charlotte Aglaé d'Orléans.

One of nine children, she was the first daughter of the family but her mother eventually returned to France to live.

Penthièvre was Maria Teresa's mother's first cousin. Charlotte Aglaé's mother was the sister of the duke's father, Louis-Alexandre Count of Toulouse. According to some contemporaries, the marriage between the duke and his wife was reportedly a happy one, to which numerous children were born.

Marie Thérèse died at the Château de Rambouillet after giving birth to Louis Marie Félicité de Bourbon, who died soon afterwards. Only two of the Penthièvre children survived into adulthood:

Francesco III d'Este, Duke of Modena

Charlotte Aglaé of Orléans

Maria Teresa's family; The Duke of Penthièvre; Prince of Lamballe; Princess of Lamballe; Mademoiselle de Penthièvre next to the Countess of Toulouse

...
Wikipedia