The Big Diamond Robbery is a 1929 American silent crime comedy film directed by Eugene Forde. The film stars Tom Mix in the lead role, with Kathryn McGuire and Frank Beal in supporting roles. It follows the story of a daring cowboy (Mix) who sets out to recover a stolen diamond, encountering a host of comedic and thrilling adventures along the way. Unlike many of Mix's westerns, this film is set in contemporary 1920s Arizona.

The Big Diamond Robbery was the last of five films Mix made for FBO Studios and also marked his final silent film. Released on April 20, 1929, it received positive reviews from critics, with praise for Mix's performance and the film's fast-paced action sequences. The film performed relatively well at the box-office for a silent film, attracting large audiences despite the growing popularity of talkies.