City Lights is a 1931 American synchronized sound romantic comedy-drama film written, produced, directed by, and starring Charlie Chaplin. While the film has no audible dialog, it was released with a synchronized musical score with sound effects. The story follows the misadventures of Chaplin's Tramp as he falls in love with a blind girl and develops a turbulent friendship with an alcoholic millionaire.

A sound film is a motion picture with synchronized sound, or sound technologically coupled to image, as opposed to a silent film. The first known public exhibition of projected sound films took place in Paris in 1900, but decades passed before sound motion pictures became commercially practical. Reliable synchronization was difficult to achieve with the early sound-on-disc systems, and amplification and recording quality were also inadequate. Innovations in sound-on-film led to the first commercial screening of short motion pictures using the technology, which took place in 1923. Before sound-on-film technology became viable, soundtracks for films was commonly played live with organs or pianos.