A new species of the copepod genus Tortanus (Atortus) (Copepoda: Calanoida), T. (A.) insularis, is described from the coastal region of Rodrigues Island, Mauritius, an isolated island in the south-western Indian Ocean. This new species can be assigned to an Indian faunal element, the recticauda species group, in the Indo-West Pacific recticauda species complex. It exhibits the closest relationship to T. (A.) recticauda recorded from the southern Red Sea and Arabian Gulf, rather than the closer distributed T. (A.) capensis, recorded from off South Africa.