Dirivultus spinigulatus sp. nov. (Copepoda: Siphonostomatoida) is described from vestimentiferans at a deep-water hydrothermal site near Lihir Island in the South Pacific. The species is characterized by several features: sexual dimorphism in the second segment of the antennule, the rostrum with lateral spines, the oral cone with four conspicuous spines, the mandible without palp, the maxilla without an axillary seta, the endopod of leg 1 with segments 1 and 2 partly fused, and leg 5 in the female represented by a conspicuous ventrally located spine but in the male by a free segment having setae. A key is included to the 11 genera of the family Dirivultidae, whose members are endemic to hydrothermal vents and cold seeps.