The Ungulinidae of the Red Sea are revised. All the species are considered to belong to Diplodonta, but only one of these can be classified with Diplodonta s.s. Five species, including D. moolenbeeki spec. nov., are provisionally placed in Diplodonta s.l. and one in the subgenus Timothynus. The latter species, recorded on the basis of a single valve from Eilat, might not belong to the autochthonous Red Sea molluscan fauna.