The Last Warning is a 1928 sound part-talkie American mystery film directed by Paul Leni, and starring Laura La Plante, Montagu Love, and Margaret Livingston. In addition to sequences with audible dialogue or talking sequences, the film features a synchronized musical score and sound effects along with English intertitles. The film apparently only survives in a cut-down edited silent version which was made for theaters that had not yet converted to sound. The soundtrack for the sound version, which was also released on sound-on-disc format, survives in private hands on Vitaphone type discs.

The Last Warning was also one of the very last part-talkie films Universal made, with roughly sixty feet of talking sequences added (only a minute or two). Its plot follows a New York producer's attempt to re-stage a play five years after one of the original cast members was murdered in the theater. The film is based on the 1922 Broadway melodrama of the same name by Thomas F. Fallon, which in turn was based on the story House of Fear by Wadsworth Camp, the father of the writer Madeleine L'Engle.

Conceived as a followup to Leni's wildly successful 1927 production The Cat and the Canary (also starring La Plante), the film was produced by Universal Pictures under Carl Laemmle. Principal photography took place in Los Angeles in the summer of 1928 on sets recycled from Universal's The Phantom of the Opera (1925). It premiered on Christmas Day 1928 before expanding in January 1929, and was released as both a part-sound film as well as a silent film; the silent is the only known extant version. It was the final film directed by Leni before his death from blood poisoning on September 2, 1929.

Response by critics to The Last Warning varied, with many praising its performances and cinematography, though several commented on its incoherent plot, and others criticized its integration of sound, feeling it presented optimally as a silent film. In 2016, Universal Pictures selected it for film restoration, using elements from two different prints owned by the Packard Humanities Institute and the Cinémathèque Française.