Collections of marine animals from the northrn Red Sea were made by Tel Aviv University and the Hebrew University of Jerusalem between 1950 and 1972, and from the southern Red Sea by the Sea Fisheries Research Station, Haifa, in 1957/58, and the Israel South Red Sea Expeditions in 1962 and 1965. This report is based on 485 specimens of spider crabs from those collections. A total of 37 species belonging to 26 genera are dealt with. The total number of species of the family Majidae now known from the Red Sea is 46, of which 12 are recorded here for the first time. One new species, Opthalmias longispinus n. sp., is described. The collection includes five species previously known only from the first record. Only seven (15%) of the species appear restricted to the Red Sea. These, in general, belong to genera occuring in the Atlantic and are, with one exception, poorly represented throughout the Indo-West Pacific and the remaining 13 (28%) occur in the Indian Ocean, principally off East Africa and in the Arabian Sea.