This introduction serves as an overview of the development of operetta and points to the neglect of operetta by many scholars of music and theatre. The editors begin by defining this genre, which is multi-faceted and often difficult to categorize. The introduction sets the stage for the following chapters by guiding the reader towards the important landmarks in the historical developments of operetta, such as those that occurred in France, Austria and London, and, in the twentieth century, in Berlin. In doing so, it also comments on notable composers and works. It concludes with some reflections on operetta reception in the twenty-first century.