The taxonomic position of a Gram-positive, non-motile, non-spore-forming coryneform, isolated from activated sludge and designated strain CAU 212(T), was investigated using a polyphasic approach. Cellular morphology, biochemical tests and chemotaxonomic investigations revealed that strain CAU 212(T) had the characteristics of the genus Corynebacterium. Comparative 16S rRNA gene sequence analysis showed that the organism formed a hitherto-unknown subline within the genus Corynebacterium. Sequence divergence values of more than 4.3 % from recognized Corynebacterium species, together with phenotypic differences, showed that the bacterium represents a previously unrecognized member of the genus Corynebacterium, for which the name Corynebacterium doosanense sp. nov. is proposed. The type strain is CAU 212(T) (=KCTC 19568(T)=CCUG 57284(T)).