Specimens of the genera Mathilda and Tuba from New Caledonia and the Loyalty Islands are studied, and compared with numerous other nominal mathildid species from the Indo-Pacific and Atlantic Oceans. Diversity is high in this region, with several species showing a much wider distribution in the Indo-Pacific than previously ascertained. Mathilda Semper, 1865 is used sensu lato, including Fimbriatella, Granulicharilda, Mathildona and Opimilda. From the study area thirteen species are diagnosed and compared, and several as yet unnamed forms that need further study are also discussed. Four new species are described, and Mathilda fusca (Okutani & Habe, 1981), previously placed in the turritellid genus Orectospira, is recognized as the largest extant member of the family Mathildidae. Tuba Lea, 1833 is also used sensu lato, including Gegania and Tubena, and is represented by two species (one described as new). Twelve Indo-Pacific species previously referred to as Mathildidae are removed from the family: Mathildona cookiana Dell, 1956 (Epitoniidae); Mathilda elegantula Angas, 1871 (Pyramidellidae ?); M. eurytima Melvill & Standen, 1896 (Cerithiidae); M. gracillima Melvill & Standen, 1901 (Capulidae); M. oppia Hedley, 1907 (Rissoidae); M. opulenta Hedley, 1907 (Cerithiidae); M. rosae Hedley, 1901 (Eulimidae); Eucharilda pleurorbis Laseron, 1951, and Opimilda protolineata Laseron, 1951 (Triphoridae); O. porrigata Laseron, 1951 (Cerithiopsidae ?); Dunkeria pulchella A. Adams, 1860, and D. scabra A. Adams, 1860 (Epitoniidae).