A Gram-negative, rod-shaped, non-spore-forming bacterium (strain NS11T) was isolated from a lichen-colonized rock surface. On the basis of 16S rRNA gene sequence similarity, strain NS11T was shown to belong to the Betaproteobacteria, and was most closely related to Herminiimonas arsenicoxydans ULPAs1T (98.8%), Herminiimonas aquatilis CCUG 36956T (98.0%) and Herminiimonas fonticola S-94T (98.0%). Major whole-cell fatty acids were C16:0, C17:0 cyclo and C16:1omega7c. Strain NS11T also contained high proportions of C10:0 3-OH and C18:1omega7c. This pattern is typical for members of the genus Herminiimonas. The results of DNA-DNA hybridization experiments and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain NS11T from the three recognized Herminiimonas species. It is therefore concluded that strain NS11T represents a novel species of the genus Herminiimonas, for which the name Herminiimonas saxobsidens sp. nov. is proposed. The type strain is NS11T (=DSM 18748T=CCM 7436T).