Marguerite Cunliffe-Owen (1859 – 1927) was a historical novelist, nonfiction author, and a syndicated newspaper columnist, under the pseudonyms La Marquise de Fontenoy and the Countess du Planty.
The daughter of Count Jules du Planty de Sourdis, she married Frederick Cunliffe-Owen. In 1885, after losing their European fortunes, the couple made a fresh start in the United States, he eventually becoming foreign editor and later society editor of the New York Tribune in 1889.
Marguerite Cunliffe-Owen published a series of biographies and novels. Several of her books dealing with the royal courts of Europe were published anonymously or under the nom de plume, La Marquise de Fontenoy, which was the name she used for a newspaper column that chronicled upper class society in a frank manner.
She was made an honorary member of the police honor legion of the New York City Police Department in recognition of her volunteer work on behalf of wounded policemen.
She died on 29 August 1927, a year after her husband's death, and left her estate to Dr. Edward F. Sutton, "for many years a member of the Cunliffe-Owen household".