Four new species of the genus Celonites Latreille, 1802 (Hymenoptera: Vespidae: Masarinae) are described from south-western Africa: heliotropii and pulcher from Namibia, kalahariensis from Namibia and the adjacent trans-Orange part (Gordonia) of the Northern Cape of South Africa, and arenarius from the north-western corner (Richtersveld) of the Northern Cape. A neotype is designated for the widespread, chiefly Namibian Celonites michaelseni von Schulthess, 1923, with which C. gariepensis Gess, 1997 is sunk into synonymy. Namibian records are given for C. andrei Brauns, C. capensis Brauns, C. clypeatus Brauns, and C. tiiniidiscutellatus Gess, all better known from South Africa. Distribution maps are given for all nine species and forage plant records are included for eight. A key to the species of Celonites occurring in Namibia is given. Keywords: Hymenoptera, Vespidae, Masarinae, Celonites, new species, Namibia, southern Africa.