Gram-negative anaerobic rods were isolated from chinchilla (Chinchilla lanigera) faeces and three strains, ST170(T), ST180 and ST28(T), were investigated taxonomically. On the basis of phylogenetic analyses and specific phenotypic characteristics, the three strains belonged to the genus Bacteroides. Phylogenetic analysis of their 16S rRNA gene sequences revealed that strains ST170(T) and ST180 formed a single cluster and a distinct line of descent. Strain ST170(T) exhibited 99.7 % 16S rRNA gene sequence similarity with strain ST180 and 95.1, 94.6 and 94.4 % 16S rRNA gene sequence similarity with Bacteroides massiliensis JCM 13223(T), Bacteroides dorei JCM 13471(T) and Bacteroides vulgatus JCM 5826(T), respectively. Strain ST28(T) also formed a distinct line of descent and exhibited the highest 16S rRNA gene sequence similarity with Bacteroides uniformis JCM 5828(T) (98.1 %). Low DNA-DNA relatedness (1 %) between strain ST28(T) and B. uniformis JCM 5828(T) clearly indicated that they belonged to different species. Analysis of hsp60 sequences also supported these relationships. The DNA G+C contents of strains ST170(T) and ST28(T) were 45.2 and 41.0 mol%, respectively. On the basis of phenotypic characteristics and phylogenetic data, two novel species, Bacteroides chinchillae sp. nov. (type strain ST170(T) = JCM 16497(T) = CCUG 59335(T)) and Bacteroides rodentium sp. nov. (type strain ST28(T) = JCM 16496(T) = CCUG 59334(T)), are proposed.