Leo Burnett Worldwide, Inc., also known as Leo Burnett Company, Inc., is an American advertising company, founded on August 5, 1935, in Chicago by Leo Burnett.

Leo Burnett was an American advertising executive and the founder of Leo Burnett Company, Inc. He was responsible for creating some of advertising's most well-known characters and campaigns of the 20th century, including Tony the Tiger, the Marlboro Man, the Maytag Repairman, United's "Fly the Friendly Skies", and Allstate's "Good Hands", and for garnering relationships with multinational clients such as McDonald's, Hallmark and Coca-Cola. In 1999, Burnett was named by Time as one of the 100 most influential people of the 20th century.