The Tygart Valley River is a major tributary of the Monongahela. It starts near the Randolph-Pocahontas county line and flows 118 miles north, eventually joining the West Fork River at Fairmont to form the Monongahela.

The Tygart Valley was named for the David Tygart family, who settled the area in 1753.

The river's valley has rich farmland and was an important travel route. During the Civil War, the area was heavily used by troops, and a major battle was won by Union forces nearby at Rich Mountain in 1861.

The upper section of the river drops steeply, making it swift-flowing. To help control the water, West Virginia's first flood-control dam was built on the Tygart Valley River near Grafton between 1935 and 1938. The river's main tributary is the Buckhannon River.