The Greenbrier River is a tributary of the New River, 162 miles (261 km) long, in southeastern West Virginia, in the United States. Via the New, Kanawha and Ohio rivers, it is part of the watershed of the Mississippi River, draining an area of 1,656 square miles (4,290 km2). It is one of the longest rivers in West Virginia.

The New River is a river which flows through the U.S. states of North Carolina, Virginia, and West Virginia before joining with the Gauley River to form the Kanawha River at the town of Gauley Bridge, West Virginia. Part of the Ohio River watershed, it is about 360 miles (580 km) long.