Original provider: Tethys Research Institute Dataset credits: Marina Costa, Amina Cesario, Maddalena Fumagalli & Giuseppe Notarbartolo di Sciara, Tethys Research Institute Chris Smeenk Eritrea Project - Yohannes Mebrahtu IMMRAC Peter Rudolph Red Sea Dolphin Project - HEPCA Abstract: Based on a review of the literature, complemented by original observations at sea made by the authors during the past 34 years, the cetacean fauna in the Red Sea appears to be composed by a total of 16 species: three Mysticetes (Bryde’s whale, Balaenoptera edeni; Omura’s whale, B. omurai; and humpback whale, Megaptera novaeangliae) and 13 Odontocetes (dwarf sperm whale, Kogia sima; killer whale, Orcinus orca; false killer whale, Pseudorca crassidens; short-finned pilot whale, Globicephala macrorhynchus; Risso’s dolphin, Grampus griseus; Indian Ocean humpback dolphin, Sousa plumbea; rough-toothed dolphin, Steno bredanensis; Indo-Pacific bottlenose dolphin, Tursiops aduncus; common bottlenose dolphin, T. truncatus; pantropical spotted dolphin, Stenella attenuata; spinner dolphin, S. longirostris; striped dolphin, S. coeruleoalba; Indo-Pacific common dolphin, Delphinus delphis tropicalis). This review presents the very first documented and confirmed sightings of B. omurai, K. sima and S. bredanensis in the Red Sea. Of all the above species, however, only nine (Bryde’s whale, false killer whale, Risso’s dolphin, Indian Ocean humpback dolphin, Indo-Pacific bottlenose dolphin, common bottlenose dolphin, pantropical spotted dolphin, spinner dolphin, and Indo-Pacific common dolphin) appeared to occur regularly in the Red Sea, the remaining seven only occurring sporadically as vagrants from the Indian Ocean. Even regular species appeared not to be uniformly distributed throughout the Red Sea, e.g., with Indo-Pacific common dolphins mostly limited to the southern portion of the region, and the Gulf of Suez only hosting the two bottlenose dolphin species and Indian Ocean humpback dolphins. No convincing evidence was found of the Red Sea occurrence of two whale species mentioned in the literature: the common minke whale, Balaenoptera acutorostrata, and the sperm whale, Physeter macrocephalus. The absence from the region of deep diving species (e.g., Ziphiidae and the sperm whale) can be explained by the geomorphology of the Straits of Bab al Mandab, with its extended shallow sill likely to discourage incursions by such species into the Red Sea. The coordinated effort and the different expertise of the authors has contributed to amend previous mistakes and inaccuracies, verify and validate specimen identification, highlight features of relevance for species taxonomy and, most importantly, draw a fundamental baseline to inform conservation of cetaceans in the Red Sea.