Genre, Greek: genos, γένος) is the term for any category of literature or other forms of art or entertainment, e.g. music, whether written or spoken, audial or visual, based on some set of stylistic criteria. Genres are formed by conventions that change over time as new genres are invented and the use of old ones are discontinued. Often, works fit into multiple genres by way of borrowing and recombining these conventions. Genre theory is a branch of critical theory.

Genre began as an absolute classification system for ancient Greek literature. Poetry, prose and performance had a specific and calculated style that related to the theme of the story. Speech patterns for comedy would not be appropriate for tragedy, and even actors were restricted to their genre under the assumption that a type of person could tell one type of story best. In later periods genres proliferated and developed in response to changes in audiences and creators. Genre became a dynamic tool to help the public make sense out of unpredictable art. Because art is often a response to a social state, in that people write/paint/sing/dance about what they know about, the use of genre as a tool must be able to adapt to changing meanings. In fact as far back as ancient Greece, new art forms were emerging that called for the evolution of genre, for example the "tragicomedy".

Genre suffers from the same ills of any classification system. Genre is useful as long as it is remembered that it is a helpful tool, to be reassessed and scrutinized, and to weigh works on their unique merit as well as their place within the genre. It has been suggested that genres resonate with people because of the familiarity, the shorthand communication, as well as the tendency of genres to shift with public mores and to reflect the zeitgeist. While the genre of storytelling has been relegated as lesser form of art because of the heavily borrowed nature of the conventions, admiration has grown. Proponents argue that the genius of an effective genre piece is in the variation, recombination, and evolution of the codes.