Horton Hears a Who! is a 2008 American Computer Generated Imagery (CGI) movie, based on the Dr. Seuss book of the same name. The fourth feature film from Blue Sky Studios, preceded in 2006 by Ice Age: The Meltdown, it will be released by 20th Century Fox. Featuring the voices of Jim Carrey, Steve Carell, Carol Burnett, and Will Arnett, the movie will be released in the USA, the UK, and Canada on March 14th, 2008. This will be the first Dr. Seuss adaptation fully animated by computer, using CGI technology. The film is rated G by the MPAA.

The film was directed by Jimmy Hayward and Steve Martino, based on a screenplay written by Ken Daurio and Cinco Paul. The film was produced by Bob Gordon, Audrey Geisel, Christopher Meledandri and Chris Wedge. Christian Kaplan was the casting director and music was provided by John Powell (Ice Age; The Meltdown). This is the second film Jim Carrey and Steve Carell have appeared in together. Their first film together was the 2003 comedy Bruce Almighty. This also marks the second Dr. Seuss adaptation in which Jim Carrey has appeared, the first being The Grinch (2000).