Bad Santa is a 2003 American Christmas black comedy crime film directed by Terry Zwigoff, written by Glenn Ficarra and John Requa, and starring Billy Bob Thornton in the title role, with a supporting cast of Tony Cox, Lauren Graham, Brett Kelly, Lauren Tom, John Ritter, and Bernie Mac. It was Ritter's last live-action film appearance before his death on September 11, 2003. The film was dedicated to his memory. The Coen brothers are credited as executive producers. The film was released in North America on November 26, 2003, and was screened out of competition at the 2004 Cannes Film Festival. It received positive reviews and was a commercial success.

An unrated version was released on DVD on March 5, 2004, and on Blu-ray on November 20, 2007, as Bad(der) Santa. A director's cut DVD was released in November 2006; it features Zwigoff's cut of the film (including an audio commentary with him and the film's editor), which is three minutes shorter than the theatrical cut and ten minutes shorter than the unrated version. A sequel, Bad Santa 2, was released on November 23, 2016, and failed to match the critical and commercial success of the original.