| South Fork Grand River | |
| Name Other: | Tributary to Grand River |
| Pushpin Map: | South Dakota#USA |
| Pushpin Map Caption: | Location of South Fork Grand River mouth |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | South Dakota |
| Subdivision Type3: | Counties |
| Subdivision Name3: | Perkins Harding |
| Length: | 143.15miles[1] |
| Discharge1 Location: | Grand River |
| Discharge1 Avg: | 115.36cuft/s at mouth with Grand River[2] |
| Source1: | Buffalo Creek divide |
| Source1 Location: | about 12 miles southwest of Buffalo, South Dakota |
| Source1 Coordinates: | 45.4542°N -103.7171°W[3] |
| Source1 Elevation: | 3500feet |
| Mouth: | Grand River |
| Mouth Location: | Shadehill Reservoir |
| Mouth Coordinates: | 45.725°N -102.2838°W |
| Mouth Elevation: | 2274feet |
| Progression: | Grand River → Missouri River → Mississippi River → Gulf of Mexico |
| River System: | Grand River |
| Tributaries Left: | Big Creek, Little Grand River, Jerry Creek, Pine Spring Creek, Graves Creek, Brush Creek, Rush Creek, Slick Creek, Sheep Creek, Boxelder Creek, Jones Creek, Bull Creek, Coal Creek, Horse Creek, Brush Creek, Skull Creek, Olean Creek, Middle Creek, Big Nasty Creek, Duck Creek, Little Nasty Creek, Lodgepole Creek |
| Tributaries Right: | Clarks Fork Creek, Eggland Creek, Prairie Dog Creek, Fisher Creek, Bar H Creek, White Hill Creek, Murphy Creek, Snake Creek, Defenbull Creek, Timber Draw Creek, Box Spring Creek, Butcher Creek |
| Bridges: | Gilbert-Hett Road, US 85, E6 Road (x2), SD 79, White Hill Road, Divide Road, SD 75, White Butte Road |
The South Fork of the Grand River is a tributary of the Grand River, approximately 90 mi (145 km) long, in South Dakota in the United States.
It rises in the Badlands of northwestern South Dakota, south of the Cave Hills in western Harding County, and flows east past Buffalo, then past several units of the Grand River National Grassland in northern Perkins County. It joins the North Fork in the Shadehill Reservoir near to form the Grand, which is a tributary of the Missouri.