Robert de Flers (Robert Pellevé de La Motte-Ango, marquis de Flers) (25 November 1872, Pont-l'Évêque, Calvados – 30 July 1927, Vittel) was a French playwright, opera librettist, and journalist.
He entered the Lycée Condorcet in 1888 where he studied law with the initial ambition of entering diplomatic service. He met and befriended fellow student and writer Marcel Proust, and that relationship had a great influence upon him. Proust exposed Flers to art, literature, and music and his interests soon switched from law to writing, journalism, and literature. The two men enjoyed a lifelong friendship.
After completing his studies, he toured throughout Asia in the mid-1890s. The event inspired his earliest writings: the novel La Courtisane Taïa et son singe vert (1896), the short story Ilsée, princesse de Tripoli (1896), and the travel narrative Vers l’Orient (1897). Upon returning to Paris, he was approached by composer Edmond Audran to write the libretto for his operetta La reine des reines. The worked premiered on 14 October 1896 at the Théâtre de l'Eldorado in Strasbourg. His next libretto was for Gaston Serpette's vaudeville-operetta Shakspeare! which premiered at the Théâtre des Bouffes Parisiens on 23 November 1899.
In 1901 de Flers married Geneviève Sardou, the daughter of Victorien Sardou. He continued to be active writing librettos. His third opera libretto, Les travaux d'Hercule (1901), marked his first collaboration with fellow playwright Gaston Arman de Caillavet and composer Claude Terrasse. Most of his remaining librettos were written with Caillavet, often for Terrasse who was their most frequent musical collaborator. Other composers for which the two men wrote librettos include André Messager, and Gabriel Pierné. The two men also wrote a French translation of Franz Lehár's The Merry Widow in 1905 which was used throughout France during the first half of the 20th century. Their last opera collaboration was for Alfred Bruneau's 1923 opera Le jardin du paradis. De Flers also wrote the librettos for Reynaldo Hahn's Ciboulette (1923) with playwright Francis de Croisset, and Joseph Szulc's Le petit choc (1923).