Operetta (German: Operette) is a 1940 musical film directed by Willi Forst and starring Forst, Maria Holst and Dora Komar. The film was made by Wien-Film, a Vienna-based company set up after Austria had been incorporated into Greater Germany following the 1938 Anschluss. It is the first film in director Willi Forst's "Viennese Trilogy" followed by Vienna Blood (1942) and Viennese Girls (1945). The film portrays the life of Franz Jauner (1832–1900), a leading musical figure in the city. It is both an operetta film and a Wiener Film.

Country girl Margit sits for the artist Sándor, from Budapest. She is fascinated and charmed by him, and agrees to accompany him to the capital, so he can complete the painting there. Disillusionment sets in, however, when Sándor wins a prize with the finished portrait and loses interest in her. Margit recognizes that her true happiness lies at home, with Pista, her faithful lover.

Vienna, Austria, late 1870s. After suffering an irreparable misfortune, the Austrian composer Johann Strauss Jr. (1825-99), the Waltz King, falls in love with a ballet dancer, which disappoints the famous operetta singer Marie Geistinger…