We describe a new species of Desmognathus from Union County, Georgia. It closely resembles D. quadramaculatus, but the two are distinguishable by adult size, body proportions, color pattern, and fixed differences at four allozyme loci. The new, smaller species is currently known from two tributaries of the Nottely River and is sympatric with D. quadramaculatus at both sites. The new form is semi-aquatic and utilizes habitats that are similar to those of D. quadramaculatus. Metamorphosis occurs at a smaller size than in D. quadramaculatus, apparently as a result of a shorter larval period. Selection on life history features may have had a role in the origin and divergence of these forms.