Deffand, Or Defiant, Marie (De Vichy-Cham-Eoxd), marquise du, an accomplished French woman, born at the chateau of Chamrond in 1697, died in Paris, Sept. 24, 1780. She was of noble birth, and was educated at a convent; but at the age of 16 she adopted skeptical opinions on religious subjects. At 20 she was married to the marquis du Deffand, from whom her indiscretions soon caused her to be separated; after which she pursued a career of fashionable dissipation, and for many years was one of the most brilliant ornaments of the court of the regent and of Louis XV. Although incapable, from a natural selfishness and want of sympathy, of entertaining the passion of love, she knew how to inspire it in others; and over the greater part of her numerous lovers, among whom, it is said, was the regent himself, her influence remained unimpaired until their dotage. She was courted by the most eminent men of the time; and when, in her 55th year, she became blind, her saloons in the convent of St. Joseph were the favorite resort of Montesquieu, Voltaire, President He-nault, D'Alembert, David Hume, and many others. At this period she became acquainted with Horace Walpole, between whom and herself a correspondence was carried on for many years.
Her latter years were marked by peevishness, and she died unhappy after unavailing efforts toward the life of a devotee. Her correspondence was first published in 1802. A new edition appeared in 1859, and two in 1864.