ESTREES, GABRIELLE D' (1573-1599), mistress of Henry IV. of France, was the daughter of Antoine d'Estrees, mar quis of Coeuvres, and Francoise Babou de la Bourdaisiere. Henry IV., who in Nov. 1 S90 stayed at the castle of Coeuvres, became violently enamoured of her. Her father married her to Nicholas d'Amerval, seigneur de Liancourt, but in Dec. 1592, Gabrielle, whose affection for the king was sincere, became his mistress. She lived with him from Dec. 1592 onwards, and bore him sev eral 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 April so, 1599. Poison was of course suspected; but her death was really caused by puerperal convulsions (eclampsia). See Gabrielle d'Estrees et la politique de Flenri IV. (1859) ; A. Desclozeaux, Gabrielle d'Estrees, Marquise de Monceaux, etc. (1889; Eng. trans. 19o7)a