Whitney Warren (January 29, 1864 – January 24, 1943)^[1] was an American Beaux-Arts architect who founded, with Charles Delevan Wetmore, Warren and Wetmore in New York City, one of the most prolific and successful architectural practices in the US.

Warren was born in New York City on January 29, 1864. He was one of nine children born to George Henry Warren I (1823–1892) and Mary Caroline (née Phoenix) Warren (1832–1901).^[2] His siblings included Lloyd Warren, who was also an architect,^[3] and George Henry Warren II,^[4] a stockbroker who was the father of Constance Whitney Warren.^[5] He was a cousin of the Goelets^{[lower-alpha 1]} and Vanderbilts^{[lower-alpha 2]} and the grandson of U.S. Representative Jonas Phillips Phoenix.^{[7][lower-alpha 3]}

In 1883, he enrolled at Columbia University to study architecture, but only stayed for one year.^[9] He was shown on official Columbia University records as a member of the class of 1885 of the School of Mines, Columbia University.^[10][11] From 1884 until 1894, Warren spent ten years at the École des Beaux-Arts in Paris. There he studied under Honoré Daumet and Charles Girault,^[12] and met fellow architecture student Emmanuel Louis Masqueray, who would, in 1897, join the Warren and Wetmore firm.^[13]

Warren returned to New York in 1894, and began practicing as an architect.^[13] One of his first clients was the lawyer Charles Delevan Wetmore. After their successful collaboration, Warren convinced Wetmore to become his partner and they organized Warren and Wetmore with Warren as the architect and Wetmore responsible for the business side of the firm.^[14]

During World War I, Warren was involved in organizing the Comité des Étudiants Américains de l'École des Beaux-Arts Paris; a student-run charity in support of the French cause. He also supported actively the claims of Italy in the Adriatic, during and after the war. He was an intimate friend of Gabriele d'Annunzio, and was appointed diplomatic representative in the United States of the "Free State of Fiume". He was the author of Les Justes Revendications de l'Italie: la Question de Trente, de Trieste et de l'Adriatique. Many of his addresses, delivered 1914-1919, were published and widely distributed.^[12]

Warren retired in 1931, but occasionally served as consultant. Warren took particular pride in his design of the new library building of the Catholic University of Leuven, which was finished in 1928. The library was severely damaged by British and German forces during World War II, but was completely restored after the war.^[14]

Two of the firm's major works were the construction of Grand Central Terminal and of the Biltmore Hotel, both in New York City.^[13]

In 1884, Warren was married to Charlotte Augusta Tooker (1864–1951)^[15] in Newport, Rhode Island.^[16] Charlotte was the eldest daughter of Gabriel Mead Tooker, a prominent New York lawyer and member of Mrs. Astor's famous "Four Hundred".^[16] She was also the cousin of Col. Clermont Livingston Best's daughter, Annie Livingston Tooker Best, wife of Elizur Yale Smith, the son of Wellington Smith, members of the Yale family.^{[17][18][19][20]} Together, they are the parents of:^[21]

• Charlotte Augusta Warren (1885–1957), who married William Greenough in 1907.^[6]
• Gabrielle Warren (1895–1971),^[22] who married Reginald Bulkeley Rives (1890–1957),^[23] a nephew of George Rives and Edward Bulkeley,^[24] in 1917.^[25]
• Whitney Warren Jr. (1898–1986),^[26][27] who was a horticulturalist and patron of the arts.^[28][29] Warren Jr. was referred to as "an overly rich bachelor operating in San Francisco"^[27] who traveled around the world.^[30]

In 1927, Warren and his brother George each inherited $2,314,143 from the estate of their uncle, Lloyd Phoenix.^[1]

Warren died after a nine-week illness on January 24, 1943, at New York Hospital in New York City.^[1] At the time of his death, Warren resided at 280 Park Avenue in New York City and was a member of the Knickerbocker Club, the Racquet and Tennis Club, and the Church and South Side Sportsmen's Clubs.^[1] After a service at St. Thomas Church, Fifth Avenue, he was buried at Island Cemetery in Newport.^[31] His widow died in 1951 and was buried alongside him in Newport.^[15]