Chauncey Addison Day, better known as Chon Day, (April 6, 1907 – 2000) was an American cartoonist whose cartoons appeared in The New Yorker and other magazines.
Born in Chatham, New Jersey, Day attended Lehigh University in 1926, where he drew for the college's humor magazine, The Burr. After one year, he left and later enrolled in 1929 at New York City's Art Students League, where he studied under Boardman Robinson, George Bridgman and John Sloan. That same year his cartoons were first published in national magazines.
His cartoon series Brother Sebastian began in 1954 in the magazine Look, where it ran for years. These cartoons were collected in several Doubleday books, Brother Sebastian, Brother Sebastian Carries On and Brother Sebastian at Large (1961), reprinted in paperback by Pocket Books.
Day described his character in the introduction to Brother Sebastian at Large:
Day received the National Cartoonists Society Gag Cartoon Award for 1956, 1962 and 1970, plus their Special Features Award for Brother Sebastian in 1969.
Day died in 2000, according to The Saturday Evening Post (May 2000), where he had been their "longest running cartoonist" for more than half a century.