Clifford's Really Big Movie is a 2004 American animated adventure comedy film based on the PBS Kids TV series Clifford the Big Red Dog, itself an adaptation of the book series of the same name by Norman Bridwell. This film was directed by Robert Ramirez, produced by Scholastic Entertainment and Big Red Dog Productions, and was originally released to theaters for a limited time by Warner Bros. Pictures on February 20, 2004.

The film takes place on "Birdwell Island" (the name of which is inspired by Norman Bridwell, the author of the books), and follows the titular dog Clifford, who decides to join a traveling animal show that will provide the winner with a lifetime supply of the dog food, after he mistakenly assumes his owners are spending too much on his dog food.

It is one of only two separate theatrically released films based on a PBS children's property (including Barney's Great Adventure), excluding the two films based on Sesame Street. Serving as John Ritter's final theatrical film role prior to his death on September 11, 2003, the film was dedicated to his memory, and also serves as the series finale for the television series.

The film grossed $3.3 million at the box office, and received mixed overall critical reviews.