Flat Top Mountain, located along the contiguous boundaries of Mercer, Raleigh, Summers, Wyoming, and McDowell counties in West Virginia, is a part of the Allegheny Front located on the southern edge of the dissected Allegheny Plateau. There are two other Flat Top Mountains, one each in Hardy and Monroe counties.

Flat Top Mountain extends over about 400 square miles between the Bluestone River; White Oak, Talley, and Guyandotte mountains; and Micajah, Indian, and Stone ridges. Within the region are tributaries of the Bluestone and New rivers and headwaters of the Guyandotte River, Elkhorn Creek, and Tug Fork.

The summit of Flat Top is a tableland of about 40 square miles above 3,000 feet, surrounded by a serrated escarpment of steep walled gorges that rises from 2,400—2,500 feet above sea level. The maximum elevation is 3,560 feet at Huff Knob near the community of Flat Top. Other elevations include Bluff Mountain (3,476), Indian Grave Mountain (3,440), Bald Knob (3,400), Rich Knob (3,400), and Pilot Knob (3,480).

Tough Guyandotte sandstone has preserved the surface of Flat Top. Much of the region is underlain by rich deposits of Pocahontas coal. Underground mining began in the 1880s when the Norfolk & Western Railroad and branch lines made shipping possible. Near the turn of the 20th century there were more than 3,000 coke ovens and 150 mines operating in the region. In recent years much of the coal has been surface-mined at about 2,800 feet above sea level.

Flat Top is forested with regrowth hardwoods. Most farm land is devoted to livestock, and also to Christmas tree farming and other uses. Other economic activities are primarily recreational, with the Winterplace ski resort, Glade Springs Resort, Flat Top Lake, and Camp Creek State Park and State Forest among the region's attractions.

Although opened in recent years by modern highways, Flat Top was historically a rural and sparsely populated region of limited access. In 1911, the population of postal communities on the summit totaled 300, or about seven people per square mile. A branch of the Buffalo Trail extended along the mountain, and in the Civil War Union and Confederate lines extended across the Alleghenies from Flat Top to Sewell to Cheat mountains. The West Virginia Turnpike (Interstate 77) and U.S. 19 cross Flat Top Mountain, with the turnpike offering spectacular views from the southern slopes of the mountain.