Powell River, river rising in Wise county, southwestern Virginia, U.S., and flowing southwest through Big Stone Gap in the Cumberland Plateau into Tennessee to enter the Clinch River at Norris Dam, 20 miles (32 km) northwest of Knoxville, Tenn. Approximately half of its total length of about 150 miles (240 km) is now an extension of Norris Reservoir, impounded by the dam. Originally called Beargrass River, it was probably renamed for Ambrose Powell, an explorer of the 1750s whose name was found carved on a tree near its bank.