"Summertime" is the name of an aria composed by George Gershwin for the 1935 opera Porgy and Bess. The lyrics are by DuBose Heyward and Ira Gershwin. A popular jazz standard, the song is in the Aeolian mode.
Gershwin began composing the song in December 1933, attempting to create his own spiritual in the style of the African American folk music of the period. It is sung multiple times throughout Porgy and Bess, first by Clara in Act I as a lullaby and soon after as counterpoint to the craps game scene, in Act II in a reprise by Clara, and in Act III by Bess, singing to Clara's baby.