Dona Diana Álvares Pereira de Melo, Princess of Orléans, 11th Duchess of Cadaval, Duchess of Anjou (born 25 July 1978), is a Portuguese noblewoman and author. She is the eldest daughter of Dom Jaime Álvares Pereira de Melo, 10th Duke of Cadaval, from his second marriage, to Claudine Marguerite Marianne Tritz.
She studied international communication at the American University of Paris. She manages the House of Cadaval's properties, which historically include the Palace of the Dukes of Cadaval in Évora, and the Muge estate in Santarém.
In the summer of 2015, the duchess collaborated with Hubert de Givenchy to open to the public an exhibit of haute couture bridal gowns in the palace church, Saint John-the-Evangelist. Chosen and arranged by Givenchy, the twelve dresses on display were originals borrowed from such designers as Yves Saint-Laurent, Balenciaga, Dior and include "The Nun" gown designed in 1972 for the marriage of the Spanish Caudillo Franco's granddaughter, Carmen Martínez-Bordiú to Alphonso XIII's grandson Alfonso de Bourbon, Duke of Cadíz, as well as the Givenchy dress Diana wore for her own 2008 wedding.