Anita O'Day (October 18, 1919 – November 23, 2006) was an American jazz singer.

Born Anita Belle Colton, O'Day was admired for her sense of rhythm and dynamics, and her early big band appearances shattered the traditional image of the "girl singer". Refusing to pander to any female stereotype, O'Day presented herself as a "hip" jazz musician, wearing a band jacket and skirt as opposed to an evening gown. She changed her surname from Colton to O'Day, pig Latin for "dough," slang for money.