Morton Jay Chiat (October 25, 1931 – April 23, 2002) was an American advertisement designer.

Chiat was born in the Bronx in New York City and grew up in Fort Lee, New Jersey. He attended Rutgers College, graduating in 1953 and inducted in its Hall of Distinguished Alumni in 2000.

In 1968, Chiat teamed up with Guy Day to form the Chiat/Day advertisement company in Los Angeles. Chiat/Day went on to create some the very memorable advertising campaigns and was named U.S. Agency of the Decade in 1989. Their clients were such powerhouses as Apple, Nike, Energizer, Nissan, Pathfinder, Infiniti, American Express, or Reebok. Three Chiat/Day campaigns, the Apple 1984 campaign, the Energizer Bunny campaign, and the Nynex Yellow Pages campaign, were chosen by Brandweek as three of the top 20 ad campaigns of the last 20 years. The "1984" Apple spot during Super Bowl XVIII has been said by many to be the event which marked the beginning of advertising as an event. In 1999, Jay Chiat was inducted into the American Advertising Federation’s Hall of Fame, the industry's greatest honor.