Labeotropheus is a genus of haplochromine cichlids endemic to Lake Malaŵi, Africa. Since its original description, surprisingly few additional species have been described, largely due to a misinterpretation of the historical taxonomic treatment of allopatric populations of Labeotropheus. Previously published evidence of genetic and morphological divergence among southern populations of Labeotropheus suggests that species diversity is underestimated. Morphometric, meristic, and color characteristics are employed to describe a new species of Labeotgropheus endemic to Mumbo Island and Thumbi West Island near the Nankumba Peninsula in southern Lake Malaŵi. The new species is distinguished from congeners by a wider body, longer pectoral fins, a shorter snout, and male nuptial coloration.