Marie Joseph Robert Anatole, Comte de Montesquiou-Fézensac (7 March 1855, Paris – 11 December 1921, Menton), was a French aesthete, Symbolist poet, art collector and dandy.
He is reputed to have been the inspiration both for Jean des Esseintes in Joris-Karl Huysmans' À rebours (1884) and, most famously, for the Baron de Charlus in Proust's À la recherche du temps perdu (1913-1927).
Robert de Montesquiou was a scion of the French Montesquiou-Fézensac Family. His paternal grandfather was Count Anatole de Montesquiou-Fezensac (1788-1878), aide-de-camp to Napoleon and grand officer of the Légion d'honneur; his father was Anatole's third son, Thierry, who married Pauline Duroux, an orphan, in 1841. With his wife's dowry, Thierry bought a Charnizay manor, built a mansion in Paris, and was elected Vice-President of the Jockey Club. He was a successful who left a substantial fortune. Robert was the last of Count Thierry's children, brothers Gontran and Aymery, and sister Élise. His cousin, Élisabeth, comtesse Greffulhe (1860-1952), was one of Marcel Proust's (1871-1922) models for the duchesse de Guermantes.
He had social relationships and collaborations with many celebrities of the Fin de siècle period, including Alphonse Daudet (1840–1897), Edmond de Goncourt (1822–1896), Eleonora Duse (1858–1924), Sarah Bernhardt (1844-1923), Gabriele d'Annunzio (1863-1938), Anna de Noailles (1876-1933), Marthe Bibesco (1886-1973), Luisa Casati (1881-1957), Jean Cocteau (1889-1963), and Maurice Barrès (1862-1923).