The Willow Ptarmigan or Willow Grouse (Lagopus lagopus) is a medium-sized bird in the grouse family and is a sedentary species that breeds across northern Eurasia, Alaska and northern Canada in birch and other forests.

The upper portion of the male is brown with a reddish neck and white wings and underside. The female lacks the brown. In winter, both the male and female plumages become completely white with a black tail. They are distinguished from the winter Ptarmigan by their greater size, thicker bill, habitat (not venturing above the treeline), and a lack of black between the eye and bill in the winter male.