The Cassin's Sparrow (Spanish: Zacatonero de Cassin), Aimophila cassinii, is a medium-sized sparrow.

This passerine bird's range is primarily along the United States/Mexico border, with a breeding range that extends through the Great Plains states up to the southwestern corner of Nebraska, and a winter range that extends well into Mexico.

The name of this bird commemorates the American ornithologist John Cassin.