A new subspecies of Hapalemur griseus has been discovered in the area of Fort-Dauphin, Madagascar. It is proposed to name it H.g. meridionalis. The animals resemble the other gentle lemurs except that they are slightly bigger. Chromosomal study shows that their karyotype differs from those of the other gentle lemurs, and a comparison permits the construction of a phylogenetic tree for the genus Hapalemur. Thus, this new subspecies is characterized by its morphology, its karyology and its geographical distribution.