The vascular flora of Big Frog Mountain, a 1288 m summit in the southeast corner of Tennessee, was the subject of a two year study. Collections from the study identified 479 taxa, representing 266 genera and 93 families. The Tennessee Department of Conservation lists 13 of these taxa as endangered, threatened, or special concern in Tennessee: <em>Agastache scrophulariaefolia</em>, <em>Coreopsis latifolia</em>, <em>Diervilla lonicera</em>, <em>Euonymus obovatus</em>, <em>Heracleum lanatum</em>, <em>Lonicera dioica</em>, <em>Melanthium hybridum</em>, <em>Panax quinquefolius</em>, <em>Prenanthes roanensis</em>, <em>Prunus virginiana</em>, <em>Scutellaria saxatilis</em>, <em>Silene ovata</em>, and <em>Thermopsis fraxinifolia</em>. <em>Coreopsis latifolia</em> was found for the first time in Tennessee. The distributions of the collected taxa were examined in an attempt to understand the phytogeographical significance of the Big Frog Mountain flora. Thirty-two taxa (6.7%) are endemic to the Blue Ridge Province or the southern Appalachians and 22 taxa (4.6%) are introduced. Three taxa have the southernmost distribution of their range on the mountain: <em>Dryopteris campyloptera</em>, <em>Prenanthes roanensis</em>, and <em>Prunus virginiana</em>. Big Frog Mountain is forested by a relatively undisturbed southern Appalachian flora. The mountain has maintained and conserved a more typically northern flora due to the extremely rugged topography and the prevailing winds acting in unison to provide high levels of rainfall and creating a cool, montane climate in the area.