A strictly anaerobic, cellulolytic strain, designated 18P13(T), was isolated from a human faecal sample. Cells were Gram-positive non-motile cocci. Strain 18P13(T) was able to degrade microcrystalline cellulose but the utilization of soluble sugars was restricted to cellobiose. Acetate and succinate were the major end products of cellulose and cellobiose fermentation. 16S rRNA gene sequence analysis revealed that the isolate belonged to the genus Ruminococcus of the family Ruminococcaceae. The closest phylogenetic relative was the ruminal cellulolytic strain Ruminococcus flavefaciens ATCC 19208(T) (<95% 16S rRNA gene sequence similarity). The DNA G+C content of strain 18P13(T) was 53.05±0.7 mol%. On the basis of phylogenetic analysis, and morphological and physiological data, strain 18P13(T) can be differentiated from other members of the genus Ruminococcus with validly published names. The name Ruminococcus champanellensis sp. nov. is proposed, with 18P13(T) (=DSM 18848(T)=JCM 17042(T)) as the type strain.