The following thirty-four new species of the pempherid fish genus Pempheris are described from the western Indian Ocean, raising the total number for the region to 47 species: P. andilana from northwest Madagascar; P. argyrea from the Seychelles; P. bineeshi from southeast India; P. bruggemanni from Réunion and Mauritius; P. connelli from KwaZulu-Natal, South Africa; P. ellipse from the south coast of Oman; P. hadra from the Republic of the Maldives; P. heemstraorum from Rodrigues, Mascarene Islands; P. hollemani from southeast Madagascar; P. ibo from Mozambique and South Africa; P. kruppi from the Gulf of Aden and Socotra; P. kuriamuria from the south coast of Oman; P. leiolepis from Chumbe Island, Zanzibar; P. megalops from the Seychelles; P. micromma from the south coast of Oman; P. muscat from the Gulf of Oman; P. orbis from the Red Sea; P. pathirana from Sri Lanka; P. peza from southern Mozambique; P. rochai from the south coast of Oman; P. rubricauda from northwest Madagascar; P. sergey from the Red Sea; P. shimoni from Kenya; P. shirleen from the Red Sea; P. smithorum from Zanzibar; P. tau from the Red Sea; P. ternay from the Seychelles; P. tilman from the Gulf of Aqaba, Red Sea; P. tiran from the Strait of Tiran, Red Sea; P. trinco from Sri Lanka; P. viridis from the Red Sea; P. wilsoni from the Gulf of Oman; P. xanthomma from the Gulf of Aden (Yemen); and P. zajonzi from the Socotra Archipelago. Many of the new species are described from single specimens or one location, indicating a need for more collecting to resolve the taxonomy of this group: we emphasize that some decisions are tentative and apply to the state of collections at present. The barcode mtDNA COI sequences for 21 of the 47 WIO species are analyzed, showing some deep divergences between species, but also several sibling species or species complexes that apparently share COI sequences. The genetic analysis is also limited by small sample sizes; more extensive genetic surveys are required to confirm the results. An appendix includes the description of the hybrid P. malabarica × P. russellii, a discussion of a complex of Pempheris in St. Brandon’s Shoals in need of further study, and underwater photographs of potential new species of Pempheris for which we have no specimens.