The Northern Harrier is the only harrier found in North America and is also known as the Marsh Hawk. It used to be considered a subspecies of the Hen Harrier, Circus cyaneus, which is found in Europe, Asia, and Africa. DNA sequencing has placed the Northern Harrier as a distinct species, but there is still some disagreement on this.

The female and male Northern Harriers have different plumage. The male is white and gray, the female brown. A great field marker is the white rump which is obvious in flight. Besides using their eye sight to locate prey, Northern Harriers use their sense of hearing. Their owl-like facial disk aids this.