The holoplanktonic family Miraciidae (Copepoda, Harpacticoida) is revised and a key to the four monotypic genera presented. Amended diagnoses are given for Miracia DANA, Oculosetella DAHL and Macrosetella A. SCOTT, based on complete redescriptions of their respective type species M. effecta DANA, 1849, O. gracilis (DANA, 1849) and M. gracilis (DANA, 1847). A fourth genus Distioculuc gen. nov. is proposed to accommodate Miracia minor T. SCOTT, 1894. The occurrence of two size-morphs of M. gracilis in the Red Sea is discussed, and reliable distribution records of the problematic O. gracilis are compiled. The first nauplius of M. gracilis is described in detail and changes in the structure of the antennule, P2 endopod and caudal ramus during copepodid development are illustrated. Phylogenetic analysis revealed that Miracia is closest to the miraciid ancestor and placed Oculosetella-Macrosetella at the terminal branch of the cladogram. Various aspects of miraciid biology are reviewed, including reproduction, postembryonic development, vertical and geographical distribution, bioluminescence, photoreception and their association with filamentous Cyanobacteria (Trichodesmium).