Buchanan County is a United States county in far western Virginia, the only county in the state to border both West Virginia and Kentucky. The county is part of the Southwest Virginia region and lies in the rugged Appalachian Plateau portion of the Appalachian Mountains. Its county seat is Grundy.

Southwest Virginia, often abbreviated as SWVA, is a mountainous region of Virginia in the westernmost part of the commonwealth. Located within the broader region of western Virginia, Southwest Virginia has been defined alternatively as all Virginia counties on the Appalachian Plateau, all Virginia counties west of the Eastern Continental Divide, or at its greatest expanse, as far east as Blacksburg and Roanoke. Another geographic categorization of the region places it as those counties within the Tennessee River watershed. Regardless of how borders are drawn, Southwest Virginia differs from the rest of the commonwealth in that its culture is more closely associated with Appalachia than the other regions of Virginia. Historically, the region has been and remains a rural area, but in the 20th century, coal mining became an important part of its economy. With the decline in the number of coal jobs and the decline of tobacco as a cash crop, Southwest Virginia is increasingly turning to tourism as a source of economic development. Collectively, Southwest Virginia's craft, music, agritourism and outdoor recreation are referred to as the region's "creative economy."