A strictly anaerobic, Gram-positive, endospore-forming bacterium, strain HY-37-4(T), was isolated from a forest-soil sample collected in Jeju, Republic of Korea. The cells were motile rods with peritrichous flagella. Strain HY-37-4(T) fermented various carbohydrates and the end products from glucose were formate, acetate and H(2). The major cellular fatty acids were C(16 : 0), C(16 : 0) 3-OH and iso-C(17 : 1) I/anteiso B. The G+C content of the DNA was 41 mol%. A phylogenetic analysis based on 16S rRNA sequence data indicated that the forest isolate was most closely related to Clostridium herbivorans, Clostridium populeti, Clostridium polysaccharolyticum and Eubacterium xylanophilum, which belong to Clostridium cluster XIVa. However, the low levels of 16S rRNA gene sequence similarity (92.3-93.9 %) with respect to these taxa indicate that strain HY-37-4(T) represents a novel species. Several phenotypic characteristics readily allowed the isolate to be distinguished from other phylogenetically related taxa. On the basis of the polyphasic evidence, strain HY-37-4(T) represents a novel taxon, for which the name Anaerosporobacter mobilis gen. nov., sp. nov. is proposed. The type strain is HY-37-4(T) (=IMSNU 40011(T)=KCTC 5027(T)=DSM 15930(T)).