A novel sulfate-reducing bacterium, strain HB1T, was isolated from an upflow anaerobic sludge blanket (UASB) reactor treating paper-mill wastewater operated at 37 °C. Cells of strain HB1T were oval to rod-shaped, 1–1.3 μm wide and 2.6–3.5 μm long and Gram-negative. The optimum temperature for growth was 28–30 °C. In the presence of sulfate, the isolate was able to grow on H2/acetate, formate, ethanol, propionate, fumarate, succinate, butyrate, crotonate, catechol, benzoate, 4-hydroxybenzoate, palmitate and stearate. The isolate only grew on H2 when acetate was added as a carbon source; when grown on formate, acetate was not required. Growth was also possible on pyruvate and crotonate without an electron acceptor. The isolate showed very poor growth on acetate. Thiosulfate and sulfate were used as electron acceptors. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain HB1T represents a novel lineage within the Deltaproteobacteria; sequence similarities between strain HB1T and members of other related genera were less than 91 %. Strain HB1T was also distinguished from members of related genera based on differences in several phenotypic characteristics. It is a member of the family Desulfobacteraceae. The major cellular fatty acids of strain HB1T were C16 : 0, iso-C15 : 0, anteiso-C15 : 0 and C14 : 0. β-Hydroxy fatty acids were also present in the range of C14 : 0 to C18 : 0, of which C16 : 0 was the most abundant. The G+C content of the DNA was 55.1 mol%. Based on physiological, biochemical and chemotaxonomic traits together with results of comparative 16S rRNA gene sequence analysis, strain HB1T is considered to represent a novel species in a new genus, for which the name Desulfatirhabdium butyrativorans gen. nov., sp. nov. is proposed. The type strain of Desulfatirhabdium butyrativorans is HB1T (=DSM 18734T =JCM 14470T).