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. It is most abundant on the plains. This is a perennial bunchgrass, growing erect to under meter-3 feet in height, and the flower glumes often assume a light brown to reddish-purple colour.
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.