New Guinea is the largest Pacific island, and the world's second largest, with a land area of about 785,000 km^2. Located north of Australia, the island was gradually shaped since the Eocene by the geologically recent sequential accretion of several island arc systems onto the northern part of the Australian Craton. This complex geological history has resulted in a tremendous biological diversity with high rates of endemism. On the other hand, the rugged mountainous landscape and lack of infrastructure has hampered scientific research in the country and for the most part Papuan biotas remain thus far only superficially known. This is the case for scorpions of the genus Hormurus Thorell, 1876 (Hormuridae Laurie, 1896; Scorpiones C. L. Koch, 1837). Although they are the dominant scorpion group in Wallacea and Melanesia, only two species are currently recognized from New Guinea and its adjacent islands. A thorough revisionary study of the Hormurus material present in the scientific collections of various museums and of a large series of specimens more recently collected led to the discovery of 16 new species, i.e. Hormurus ancylolobus Monod & Prendini, sp. nov.; Hormurus araiaspathe Monod & Prendini, sp. nov.; Hormurus barai Monod, Iova & Prendini, sp. nov.; Hormurus cameroni Monod, Austin & Prendini, sp. nov.; Hormurus hypseloscolus Monod & Prendini, sp. nov.; Hormurus krausi Monod & Prendini, sp. nov.; Hormurus maiwa Monod & Prendini, sp. nov.; Hormurus menapi Monod & Prendini, sp. nov.; Hormurus muyua Monod & Prendini, sp. nov.; Hormurus oyatabu Monod & Prendini, sp. nov.; Hormurus oyawaka Monod & Prendini, sp. nov.; Hormurus sibonai Monod & Prendini, sp. nov.; Hormurus slapcinskyi Monod & Prendini, sp. nov.; Hormurus sporacanthophorus Monod & Prendini, sp. nov.; Hormurus tagula Monod & Prendini, sp. nov.; Hormurus yela Monod & Prendini, sp. nov. Fully illustrated descriptions of these new taxa are presented in the present contribution, as well as a redescription of Hormurus papuanus Kraepelin, 1914. Hormurus species are characterized by relatively few diagnostic external characters which hampers species differentiation. However, the unusual interspecific diversity of hemispermatophores observed in Papuan taxa partially alleviate this issue and enable reliable species discrimination. The position of the laminar hook is particularly variable and is correlated with the elongation of the female genital operculum which also shows an atypical diversity for the genus. This interdependence strongly suggests genital coevolution driven by a lock-and-key mechanism. This would be the first such case reported for the order Scorpiones Koch, 1837. Multivariate and geometric morphometric analyses were carried out to visually emphasize subtle interspecific differences in external morphology and hemispermatophore morphology. Additionally, the correlation between hemispermatophore laminar hook position and shape of the female genital operculum was assessed statistically and comments are provided concerning potential mechanisms underlying the coevolutionary process.