The Elk River is a 35.2-mile-long (56.6 km)[1] tributary of the Neosho River in southwestern Missouri and northeastern Oklahoma in the United States. Its tributaries also drain a small portion of northwestern Arkansas. Via the Neosho and Arkansas rivers, the Elk is part of the Mississippi River watershed.
The Elk is formed by the confluence of Big Sugar Creek and Little Sugar Creek at Pineville, Missouri, and flows generally westward through McDonald County, Missouri, past the town of Noel, into Delaware County, Oklahoma, where it meets the Neosho River. Most of the river's course in Oklahoma is part of the Grand Lake o' the Cherokees, an impoundment formed by Pensacola Dam on the Neosho.