Diacyclops bicuspidatus lucanus n.ssp. is described from the phreatic freshwater network of Lucania (South Italy). Among the members of the “bicuspidatus” complex, the new subspecies is closely related to D. bicuspidatus odessanus (Schmankevitch, 1875) by the structure and the armature of the antennula of the female. From this subspecies, as well as from the others in the same group, D. bicuspidatus lucanus n.ssp. differs mainly by the remarkably elongated caudal rami and the unusual length ratio between innermost and outermost furcal setae.