Dean Cornwell (Louisville, Kentucky, 1892 – New York City, 1960) was an American illustrator and muralist whose oil paintings often appeared in popular magazines and books, in advertisements and in posters supporting the war effort. For much of the first half of the twentieth century he was a dominant figure in American illustration, and at the height of his popularity he was nicknamed the "Dean of Illustrators".
He trained in Louisville and Chicago, where he worked for newspapers and studied at the Art Institute. In 1915 he moved to New Rochelle, an artist colony near New York, and later travelled to London as an apprentice to Frank Brangwyn, whose handling of the human figure and bold outlines shaped his development. His illustrations accompanied the fiction of writers such as Ernest Hemingway, Edna Ferber and W. Somerset Maugham in Cosmopolitan, Harper's Bazaar and Redbook.
Cornwell regarded magazine illustration as ephemeral and sought lasting work in mural painting. He won the competition to decorate the central rotunda of the Los Angeles Public Library with scenes of California history, and further commissions followed, including the Lincoln Memorial Shrine in Redlands and a mural for the former Eastern Airlines building in New York. He presided over the National Society of Mural Painters from 1953 to 1957.
His legacy lies chiefly in twentieth-century American illustration and in his public murals.