Several studies of the ecology of mesopelagic fishes off Hawaii published in the 1970s and 1980s reported the existence of as many as two undescribed species in the Pacific Ocean. Diagnosed primarily on the basis of postorbital and accessory orbital photophore size and size at maturity, three new species are described: P. liemi, new species, and P. tantillux, new species, both endemic to tropical and subtropical Indo-Pacific water masses, and P. lucingens, new species, a species distributed in the subtropical and tropical Pacific and South Atlantic oceans. Photostomias liemi and P. tantillux represent smaller forms, with females maturing at standard lengths less than 70 mm, making these species the smallest sexually mature stomiids. Despite the analysis of some 35 morphometric and meristic characters, females of P. liemi are indistinguishable from females of P. atrox. The current study brings the total number of valid species of Photostomias to six. A key to these six species is provided.