La serva padrona (The Servant Turned Mistress) is an opera buffa by Giovanni Battista Pergolesi (1710–1736) to a libretto by Gennaro Federico, after the play by Jacopo Angello Nelli. The opera is only 45 minutes long and was originally performed as an intermezzo between the acts of a larger serious opera. (The same libretto was set by Giovanni Paisiello in 1781.)

Source: La serva padrona – Wikipedia