Aristida purpurea is a species of grass native to North America which is known by the common name purple three-awn.

This grass is fairly widespread and can be found across the western two thirds of the United States, much of southern Canada and parts of northern Mexico.

This is a perennial bunchgrass, growing erect to under a meter-3 feet in height, and the flower glumes often assumes a light brown to reddish-purple color.

There are several varieties with overlapping geographical ranges.

This is not considered to be a good graze for livestock because the awns are sharp and the protein content of the grass is low.