American Top 40 is an internationally syndicated, independent song countdown radio program created by Casey Kasem, Don Bustany, Tom Rounds, and Ron Jacobs. The program is currently hosted by Ryan Seacrest and presented as an adjunct to his weekday radio program, On Air with Ryan Seacrest.

Kemal Amin "Casey" Kasem was an American disc jockey, actor and radio presenter, who created and hosted several radio countdown programs, notably American Top 40. He was the first actor to voice Shaggy Rogers in the Scooby-Doo franchise and Dick Grayson/Robin in Super Friends (1973–1985).