Idomacromia jillianae sp. nov. (holotype ♀: Uganda, Kabale District, Ruhija, 1°02′59″S, 29°45′29″E, 2,100 m a.s.l., 24 v 2003) is described on the basis of two females from Bwindi Impenetrable National Park, Uganda, and compared with the known species of this elusive genus.