A gall midge that attacks citrus flower buds in south-western Japan is redescribed under the name Contarinia okadai (Miyoshi) comb. n. and is compared with C. citri Barnes, which was originally described from cultivated citrus in Mauritius. C. okadai, for which a neotype is designated, is distinguished from C. citri by morphological characters of the adult males and females and of the larvae. The known host-plants, biology and distribution of C. okadai are recorded, and new Japanese and English names for the species are proposed. The status of records of C. citri from Sicily, Cyprus, Israel, India, China and Hong Kong is discussed, and the need for further taxonomic research is stressed.