A survey of Ceratocystis species infecting wounds on non-native Acacia mearnsii and Eucalyptus spp. in Kenya, Malawi, South Africa and Tanzania resulted in the identification of eight species of which six were new to science. All identifications were based on morphology and DNA sequence data of the ribosomal RNA Internal Transcribed Spacer region, including the 5.8S operon as well as partial sequences of the β-tubulin and the Transcription Elongation Factor 1α genes. Ceratocystis moniliformis was found for the first time in Tanzania, while the wilt pathogen C. albifundus was commonly found on A. mearnsii in Kenya, South Africa and Tanzania. The undescribed Ceratocystis spp. are provided with the names C. zombamontana sp. nov., C. polyconidia sp. nov., C. tanganyicensis sp. nov., C. obpyriformis sp. nov., C. oblonga sp. nov. and Thielaviopsis ceramica sp. nov. All species introduced in this study are pathogenic on the hosts from which they were isolated.