The Vermillion River is a tributary of the Missouri River, 96 miles (154 km) long, in eastern South Dakota in the United States. The origin of the river name is Waséoyuze, Lakota for "place where vermilion is obtained". It is formed by the confluence of the East Fork Vermillion River and West Fork Vermillion River. The East Fork, approximately 103 mi long, rises in Lake Whitewood in Kingsbury County on the Coteau des Prairies. The West Fork, approximately 108 mi long, 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 and 5 mi south of Vermillion. Its tributaries include White Stone Creek and Baptist Creek. The Vermillion River drains about 2180 sqmi 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.