The Monongahela National Forest is the only national forest that is completely within the boundaries of West Virginia. The first land was purchased in 1915, and on April 28, 1920, it became the Monongahela National Forest by presidential proclamation.

In the late 19th and early 20th century, logging and timber operations had removed much of the hardwood stands of the Allegheny Mountains, causing serious ecological damage to these mountains and erosion along the streams. In March 1907, the land along the banks of the Monongahela River was devastated by flooding. As a result of this damage and damage to woodlands and streams in other areas of the United States, Congress enacted the Weeks Law in 1911 which authorized the federal government to cooperate with the various states to purchase land for the protection of the watersheds of navigable streams. Through other federal legislation, the purposes of the national forests were extended to include reforestation and timber production, wildlife management, and outdoor recreation.

The Monongahela National Forest is managed by the U.S. Forest Service, with the supervisor's office in Elkins and district offices in Parsons, Richwood, Bartow, Marlinton, Petersburg, and White Sulphur Springs. Tourist centers are maintained near Cranberry Glades and at Seneca Rocks. The forest now includes more than 920,000 acres in 10 counties, extending from Preston in the north to Greenbrier in the south. The forest also includes extensive land in Grant, Tucker, Pendleton, Randolph, Pocahontas, Webster, and Nicholas counties, along with 11 acres in Barbour County. The forest is the largest geographic entity in West Virginia, covering almost six percent of the total area of the state. Three state parks, Canaan Valley Resort, Watoga, and Blackwater Falls, as well as two state forests, Seneca and Calvin W. Price, are inside the national forest. Timber, grazing, land uses, and minerals continue to provide revenue to the state and federal governments.

The Civilian Conservation Corps was active within the Monongahela National Forest from the creation of the Corps in 1933 until its termination in 1942. There were 21 CCC camps in the forest. Their projects included the construction of roads and trails, forest management, fire protection, and other conservation efforts. The roads and trails built by the CCC still provide the public with access to remote wilderness areas.

There are eight federally designated wilderness areas in the forest, at Otter Creek, Dolly Sods, Laurel Fork North, Laurel Fork South, Cranberry, Roaring Plains West, Big Draft, and Spice Run Wilderness. There is one National Recreation Area, Spruce Knob-Seneca Rocks. There are caves at Smoke Hole and Seneca Caverns, tracts of virgin timber at Gaudineer Knob and several other locations, botanical gardens at Cranberry Glades, and wilderness trails at Dolly Sods. The Highland Scenic Highway is a designated National Scenic Byway that extends 43 miles from Richwood to north of Marlinton. The Canaan Valley National Wildlife Refuge is the largest contiguous high-elevation wetlands complex in West Virginia.

The forest also contains the Fernow Experimental Forest in Tucker County, maintained by the Forest Service to study hardwood forests management. A 2012 study examined old deeds and surveys of land parcels that are now part of the national forest. In examining the "witness trees" used to describe property boundaries, researchers determined that white oak was once the most common tree, covering an estimated 26 percent of the early forest. Other common trees were sugar maple (19 percent), American chestnut (three percent), and red spruce (two percent).

The Monongahela National Forest encompasses the high mountain country of West Virginia, including Spruce Knob, at 4,861 feet the state's highest point. Many major rivers find their headwaters within the forest, including the Elk, Gauley, Greenbrier, Potomac, Cheat, and the Monongahela itself. Seneca Rocks, one of West Virginia's best-known landmarks, is among the scenic wonders of this great upland empire. Located within a day’s drive of nearly half the nation’s population, the forest is a popular tourism attraction, particularly for hunting, fishing (notably fly fishing), hiking, and mountain biking.

In 2023, the Monongahela National Forest was selected to provide the U.S. Capitol Christmas Tree, or “People’s Tree,” for the third time, including the first harvested tree in 1970 and again in 1976.