Guy Day (July 30, 1930 – January 16, 2010) was an American advertising executive who cofounded Chiat/Day with Jay Chiat in 1968.
The agency went on to do memorable work for Apple Computer, including the Macintosh "1984" Super Bowl commercial.
Day founded an agency called Faust/Day with Tom Faust.
Day won a coin toss to see who would be the president of the new agency.
Day had two sons, Cameron and Bill, who also work in advertising and a daughter, Colleen.