Overture (from French ouverture, lit. "opening") is a music instrumental introduction to a ballet, opera, or oratorio in the 17th century. During the early Romantic era, composers such as Beethoven and Mendelssohn composed overtures which were independent, self-existing, instrumental, programmatic works that foreshadowed genres such as the symphonic poem. These were "at first undoubtedly intended to be played at the head of a programme".

The idea of an instrumental opening to opera existed during the 17th century. Peri's Euridice opens with a brief instrumental ritornello, and Monteverdi's L'Orfeo (1607) opens with a toccata, in this case a fanfare for muted trumpets. More important was the prologue, consisting of sung dialogue between allegorical characters which introduced the overarching themes of the stories depicted.