We revised the species of the genus Pristomerus Curtis, 1836 in the Afrotropical Region. Fortynine species are recognized, of which 31 are newly described. The following new species are described: P. afrikaner, P. aka, P. babinga, P. bemba, P. dikidiki, P. herero, P. hutu, P. kagga, P. khoikhoi, P. kuku, P. masai, P. mbaka, P. mbama, P. mboum, P. nzakara, P. protea, P. restio, P. san, P. sara, P. sotho, P. swahili, P. teke, P. tutsi, P. venda, P. wolof, P. xhosa, P. yakoma, P. yangere, P. yoccolo, P. zande and P. zulu spp. nov. New synonyms: P. africator, P. cunctator and P. luteolus are new junior synonyms of P. pallidus. New records: new host records are reported for the widespread P. pallidus; new country-level distribution records are added for P. bullis, P. keyka, P. kelikely and P. pallidus; and reports of Trathala concolor and P. veloma in South Africa are shown to have been erroneous. An illustrated dichotomous key to females is provided; an online Lucid interactive matrix key is also available at www.waspweb.org. Finally, the ecological and geographical correlates of colour patterns exhibited by Pristomerus in the Afrotropical region are discussed.