A new species of xanthid crab, Actaea grimaldii, is described from the coral reefs of Papua New Guinea. This species has a distinctive red and white coloration and is closest to Actaea spinosissima Borradaile, 1902, from the Indian Ocean. However, the new species can be distinguished by the arrangement of spines on the carapace, chelipeds and ambulatory legs, and the structure of the male gonopods. Actaea grimaldii sp. nov. has also been confused with A. polyacantha (Heller, 1861), but differs markedly in the carapace armature.
Crustacea, Xanthidae, Papua New Guinea, Actaea, new species.