An arsenite-oxidizing bacterium, designated strain ULPAs1(T), was isolated from industrial sludge heavily contaminated with arsenic. Cells of this isolate were Gram-negative, curved rods, motile by means of a polar flagellum. The strain was positive for oxidase and catalase activities, was able to reduce nitrate to nitrite, used acetate, lactate and peptone as organic carbon sources under aerobic conditions and was able to oxidize arsenite (As[III]) to arsenate (As[V]). 16S rRNA gene sequence analysis and the absence of dodecanoic fatty acids suggested that this strain represents a member of the genus Herminiimonas of the family Oxalobacteraceae, order Burkholderiales in the Betaproteobacteria. Genomic DNA-DNA hybridization between strain ULPAs1(T) and Herminiimonas fonticola S-94(T) and between strain ULPAs1(T) and Herminiimonas aquatilis CCUG 36956(T) revealed levels of relatedness of <10 %, well below the recommended 70 % species cut-off value. Thus, strain ULPAs1(T) (=CCM 7303(T)=DSM 17148(T)=LMG 22961(T)) is the type strain of a novel species of Herminiimonas, for which the name Herminiimonas arsenicoxydans sp. nov. is proposed.