A new genus and species of Clupeidae, Chasmoclupea aegyptica, is described from early Oligocene fluviatile deposits of the Jebel Qatrani Formation in the Fayum, Egypt. The new species is preserved in three dimensions, allowing details of the skull roof, as well as lateral skull bones, to be seen. The new species is considered to be most closely related to the Alosinae and Clupeinae. This is the first record of a clupeomorph fish from Oligocene freshwater deposits of Africa. Most clupeomorph fishes are preserved in marine or lacustrine sediments, and it is only the rare preservation of this riverine fossil, as an articulated specimen, that has allowed it to be identified as a clupeomorph.