The Tygart Valley River is a major tributary of the Monongahela River. The Tygart has its source on Valley Mountain near the Randolph-Pocahontas county line in West Virginia. With its tributaries the Tygart drains 1,329 square miles and parts of nine counties, on its way to join the West Fork River near Fairmont, thus forming the Monongahela. The Tygart drops about 3,000 feet in the 118 miles from its source to its mouth. The greatest fall occurs in Randolph County, where the upper Tygart is a swift-flowing stream. The river bisects Randolph County from south to north, paralleled most of the way by U.S. 219-250. The river's valley includes much fine farmland, settled early in the history of Western Virginia.

The Tygart flows in a north-northwesterly course as it runs through Valley Head, Huttonsville, Mill Creek, Beverly, Elkins, Norton, Belington, Philippi, and Grafton. Northwest of Elkins, the river passes through a gap between Rich Mountain and Laurel Mountain. The main tributary of the Tygart is the Buckhannon River, which joins the Tygart upstream from Philippi.

In a reversal of the usual pattern, the Tygart Valley was named before the river, for the David Tygart family who settled with the Robert Files family south of present Beverly in 1753. The river was subsequently named for the valley and has been identified by several other names in the 250 years since its settlement. It was once frequently referred to as the East Fork of the Monongahela River.

The river valley has a long, rich history, dating from the days of early settlement and the Indian wars. The upper valley is a natural thoroughfare, occupied historically by the Staunton-Parkersburg Turnpike. The turnpike was traversed by Northern and Southern troops in the Civil War, and in 1861 a major battle was fought at nearby Rich Mountain. West Virginia's first flood-control dam was built on the Tygart Valley River near Grafton in 1935-38.