A new species of ant, Solenopsis enigmatica, is described from 2 dealate queens and 3 workers collected from nests of Pheidole antillana Forel in rainforest on the island of Dominica, West Indies. The queen of S. enigmatica is similar to that of another inquiline, S. phoretica Davis and Deyrup, known only from 1 queen collected in Florida. The 2 species differ in mandibular dentition and other ways. Worker S. enigmatica do not closely resemble those of other known species. They lack clypeal carinae, have short antennal scapes, and have long, coarse hairs arising from conspicuous punctures. The presence of workers suggests that S. enigmatica might be a temporary nest parasite, but many questions remain about the relationship of this species to its host.