Ninety-eight species pertaining to 19 genera of stylasterid hydrozoans are described and illustrated from the New Caledonian EEZ, which, in addition to New Caledonia, also includes the Grand Passage, Loyalty Islands, northern Norfolk Ridge, Chesterfield Islands, Lord Howe Seamount Chain, and Lansdowne Bank. Fifty-seven of the species and two of the genera are described as new, bringing the known total number of Recent (living) stylasterid species and genera to 314 and 29, respectively, and making this region the most species- rich in the world. Four new combinations (Leptohelia microstylus, Inferiolabiata cervicornis, Stylaster sinuosus, and Paraconopora anthohelia) and one synonymy are also proposed. A new genus and species of calcified hydractiniid, Distichozoon dens, is also described. A key to all Recent stylasterid genera is provided as well as tabular and dichotomous keys to the species of the larger genera represented in the region. The study was based on specimens collected from 689 stations on 35 campagnes made by the MNHN and IRD. The adaptive advantages of calcification, the gastrostyle, the ring palisade, and dactylostyles are discussed. A review of polychaete commensalism with stylasterids is given, five polychaete families now known to have species being obligate commensals of stylasterids. A majority of the species is known only from the New Caledonian region but 30 species are also known from the southern Norfolk Ridge, the numerous seamounts of this ridge appearing to be the axis of biodiversity of this family. Only four species have broader distributions in the cold temperate southern hemisphere. Most species were found between 200 and 700 m, the deepest at 1258 m.