The Great Dictator is a 1940 American political satire comedy-drama film written, directed, produced, scored by and starring British comedian Charlie Chaplin, following the tradition of many of his other films. Having been the only Hollywood filmmaker to continue to make silent films well into the period of sound films, this was Chaplin's first true sound film.
The Great Dictator was the first true sound film. 
It was stated the film was Chaplin's first true sound film, but that Chaplin made silent films well into the sound film period, so this film could not be the first sound film, only Chaplin's first sound film. 