The grasslands, deserts, shrublands, savannas, woodlands, open forests, and alpine tundra of western North America where livestock grazed were collectively referred to as ‘range’ in the nineteenth century. Today these ecosystems are often referred to as rangelands. In the United States, rangelands comprise about 1/3rd of the total land area, mostly in the 17 western states. Large areas of rangeland also occur in Canada and Mexico. Rangelands provide numerous products, values, and ecosystem services including wildlife habitat, clean air, clean water, recreation, open space, scenic beauty, energy and mineral resources, carbon sequestration, and livestock forage. This chapter describes rangeland ecoregions in western North America.