The Cat in the Hat (also known as Dr. Seuss' The Cat in the Hat) is a 2003 American fantasy comedy film directed by Bo Welch in his directorial debut and written by Alec Berg, David Mandel and Jeff Schaffer. Loosely based on Dr. Seuss's 1957 book of the same name, it was the second and final live-action feature-length Dr. Seuss adaptation after How the Grinch Stole Christmas (2000). The film stars Mike Myers in the title role along with Alec Baldwin, Kelly Preston, Dakota Fanning, Spencer Breslin, Amy Hill and Sean Hayes in supporting roles.

Production on the film began in 1997 with Tim Allen originally cast in the title role. After Allen dropped out due to scheduling conflicts with The Santa Clause 2 (2002), the role went to Myers. Filming took place in California and lasted three months from October 2002 to January 2003. As with the previous Dr. Seuss adaptation, many new characters and subplots were added to the story to bring it up to feature-length.

The Cat in the Hat was released in theaters on November 21, 2003 in the United States by Universal Pictures and internationally by DreamWorks Pictures. It received extremely negative reviews from critics, who criticized the humor, the designs of the Cat and Thing One and Thing Two, the performances, and lack of faithfulness to the original story. It underperformed at the box office, grossing $133.9 million against a budget of $109 million. The Cat in the Hat appears on several lists of the worst films ever made. Seuss's widow, Audrey Geisel, was dissatisfied with the film and prohibited any further live-action adaptations of her husband's works, resulting in the cancellation of a sequel based on The Cat in the Hat Comes Back. Beginning with Horton Hears a Who! (2008), all Dr. Seuss film adaptations have since been produced using computer animation.In March 2012, an animated remake was announced by Universal and Illumination, but never came to fruition. As of January 2018, that remake is once again in development, now at Warner Bros. Pictures Animation.