Cedar River National Grassland is a National Grassland located in Sioux County and Grant County in southern North Dakota, United States. It has a land area of 6,717 acres (2,718 ha). The portion in Sioux County lies within the Standing Rock Indian Reservation. Within the grassland are topographic features such as level plains and rolling hills. Dry streams and some small flowing streams exist throughout the Grasslands.
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 (shared with Grand River National Grassland) in Lemmon, South Dakota.