| Vermillion River | |
| Map: | File:Vermillion river SD map 1.jpg |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | South Dakota |
| Subdivision Type5: | Cities |
| Subdivision Name5: | Vermillion, SD, Centerville, SD |
| Length: | 96miles |
| Discharge1 Location: | Vermillion |
| Discharge1 Avg: | 440cuft/s[1] |
| Source1: | Confluence of the East Fork Vermillion River and West Fork Vermillion River |
| Source1 Location: | Parker Township in Turner County, near Parker, South Dakota |
| Source1 Coordinates: | 43.3941°N -97.069°W |
| Mouth: | Missouri River |
| Mouth Location: | Fairview Township in Clay County, near Vermillion, South Dakota |
| Mouth Coordinates: | 42.733°N -96.8903°W |
| Basin Size: | 2180sqmi |
The Vermillion River is a tributary of the Missouri River, 96 miles (154 km) long,[2] in eastern South Dakota in the United States. The origin of the river name is Waséoyuze, Lakota for "place where vermilion is obtained".[3]
It is formed by the confluence of the East Fork Vermillion River and West Fork Vermillion River. The East Fork, approximately long,[2] rises in Lake Whitewood in Kingsbury County on the Coteau des Prairies. The West Fork, approximately long,[2] rises in Miner County. Both forks flow south, roughly parallel, joining east of Parker. The combined river flows south and joins the Missouri east of the James River Highlands[4] and 5miles south of Vermillion. Its tributaries include White Stone Creek and Baptist Creek. The Vermillion River drains about of the southwestern edge of the Coteau des Prairies. Approximately once per 3.5 years, the Vermillion runs dry.
The Vermillion is a north-south river situated between the Big Sioux River and James River.[4]