GABRIELLE D ESTREES' (1573-1599), mistress of Henry IV. of France, was the daughter of Antoine d'Estrees, marquis of Cceuvres, and Francoise Babou de la Bourdaisiere. Henry IV., who in November 1590 stayed at the castle of Coeuvres, became violently enamoured of her. Her father, anxious to save his daughter from so perilous an entanglement, married her to Nicholas d'Amerval, seigneur de Liancourt, but the union proved unhappy, and in December 1592, Gabrielle, whose affection for the king was sincere, became his mistress. She lived with him from December 1592 onwards, and bore him several children, who were recognized and legitimized by him. She possessed the king's entire confidence; he willingly listened to her advice, and created her marchioness of Monceaux, duchess of Beaufort (1597) and Etampes (1598), a peeress of France. The king even proposed to marry her in the event of the success of his suit for the nullification by the Holy See of his marriage with Margaret of Valois; but before the question was settled Gabrielle died, on the 10th of April 1599. Poison was of course suspected; but her death was really caused by puerperal convulsions ( eclampsia). See Adrien Desclozeaux, Gabrielle d'Estrees, Marquise de Monceaux, eec. (Paris, 1889).