Dean Cornwell was an American illustrator and muralist. His oil paintings were frequently featured in popular magazines and books as literary illustrations, advertisements, and posters promoting the war effort. Throughout the first half of the 20th century he was a dominant presence in American illustration. At the peak of his popularity he was nicknamed the "Dean of Illustrators".

Cornwell was born in Louisville, Kentucky. His father, Charles L. Cornwell, was a civil engineer whose drawings of industrial subjects fascinated Cornwell as a child. He began his professional career as a cartoonist for the Louisville Herald. Soon thereafter he moved to Chicago, where he studied at the Art Institute and worked for the Chicago Tribune. In 1915 he moved to New Rochelle, New York, a well known artist colony, and studied in New York City under Harvey Dunn at the Art Students League of New York. Eventually he traveled to London to study mural painting as an apprentice to Frank Brangwyn.

Cornwell's paintings were in Cosmopolitan, Harper's Bazaar, Redbook, and Good Housekeeping magazines, illustrating the work of authors including Pearl S. Buck, Lloyd Douglas, Edna Ferber, Ernest Hemingway, W. Somerset Maugham, and Owen Wister. He painted murals for the Los Angeles Public Library, the Lincoln Memorial Shrine in Redlands, California, the Eastern Airlines Building (now 10 Rockefeller Plaza), executed Federal Art Project murals in two post offices, Chapel Hill, North Carolina and Morganton, North Carolina, with other murals in the Warwick New York Hotel in New York City, the New England Telephone headquarters building in Boston, the Davidson County Courthouse and Sevier State Office Building in Tennessee, and the Centre William Rappard in Geneva, Switzerland. His mural for the Los Angeles Public Library was a rendering of the history of California. Cornwell's Feb 1953 cover of a riverboat for True Magazine was later made into a US Postage stamp as part of the USPS's 2001 American Illustrators series.

Cornwell taught and lectured at the Art Students League in New York. He served as president of the Society of Illustrators from 1922 to 1926, and was elected to its Hall of Fame in 1959. In 1934, he was elected into the National Academy of Design as an Associate Academician, and became a full Academician in 1940. He served as President of the National Society of Mural Painters from 1953 to 1957.

He died in New York City.