Leachia is a cosmopolitan tropical/temperate genus of ‘glass’ squids (Cranchiidae) whose taxonomy has been plagued with instability typical of the family. Eight species are currently believed to exist worldwide, including some not yet described. This review assesses the Pacific taxa, describes a novel species, L. separata, and provides updated diagnoses for the other Pacific species. Type material and original descriptions are compared, and brief remarks provided on the Atlantic taxa. The most useful characters for identifying Leachia species appear to be the number of ocular photophores and the configuration of the ventral cartilaginous strips and associated tubercles on the mantle, with arm and sucker-ring dentition also proving useful in some taxa. Further work on the genus is needed, ideally including molecular tools.