Ecologists use the term swamp to designate a wetland dominated by woody vegetation, trees, and shrubs. Swamps are the most common type of wetland in West Virginia. They are also the most diverse and most variable and include some of the rarest plant communities in the state.

At low elevations in West Virginia, swamps are typically associated with the backwaters of river floodplains. Characteristic tree species in these swamps include red maple, silver maple, river birch, ash, sweet gum, sycamore, and pin oak. In contrast, swamps of high-elevation headwaters are more often dominated by evergreen trees such as red spruce and hemlock. Shrub swamps are found at both low and high elevations. Dominant shrub species in these habitats include alders, silky dogwood, buttonbrush, glade St. John's wort, and swamp rose.

One of West Virginia's most extensive swamps is in western Greenbrier County in the vicinity of Rupert. Here the broad floodplain of the Meadow River supports thousands of acres of pin oak forest and alder shrub swamps.

The balsam fir swamps in the Allegheny highlands of Pocahontas, Randolph, and Tucker counties are among West Virginia's most unusual and most threatened plant communities. Here at the southern extent of its distribution, balsam fir is considered rare and is mostly restricted to swamps where it grows with red spruce. Blister Swamp was named after the original balsam fir, commonly called "blister pine," but the species was eliminated from the site by grazing. Restoration of balsam fir to this site is currently being attempted, but now an insect pest, the balsam wooly adelgid, threatens the species.