The holotype female, allotype male and nest are described of a new species of social wasp, Mischocyttarus (Kappa) santacruzi (Hymenoptera, Vespidae) from Atlantic coastal forest, Bahia, State, eastern Brazil. Morphologically the species is close to M. (Kappa) adolphi Zikán.
Hymenoptera; Vespidae; Mischocyttarus; social wasp; Brazil; Atlantic forest