Little Missouri National Grassland is a National Grassland located in western North Dakota, USA. At 1,033,271 acres (418,150 ha), it is the largest grassland in the country. Enclaved within its borders is Theodore Roosevelt National Park, which is managed by the National Park Service (and therefore not included in the preceding statistics). The Little Missouri National Grasslands was once a part of the Custer National Forest, but is now a part of the Dakota Prairie Grasslands, a National Forest unit consisting entirely of National Grasslands. A predominant feature of the grassland is colorful and beautiful badlands, a rugged terrain extensively eroded by wind and water. It is a mixed grass prairie, meaning it has both long and short grass.
The boundaries of the grasslands on certain maps can be misleading. Within the boundaries of the national grassland are significant portions of state-owned and privately owned land, much of it leased by cattle ranchers for grazing. Overall, in descending order of land area, it is located in parts of McKenzie, Billings, Slope, and Golden Valley counties.
White Butte, North Dakota's highest point, is located in the extreme southeast corner of the grassland, south of the town of Amidon.
The grassland is administered by the Forest Service as part of the Dakota Prairie Grasslands from offices in Bismarck, North Dakota. There are local ranger district offices in Dickinson and Watford City.