Four strains of Gram-staining-positive, anaerobic rods were isolated from the faeces of western lowland gorillas (Gorilla gorilla gorilla). Three strains, KZ01(T), KZ02 and KZ03, were isolated at the Kyoto City Zoo, Japan, and one strain, GG02, was isolated in the Moukalaba-Doudou National Park, Gabon. These strains were investigated taxonomically. These strains belonged to the Lactobacillus reuteri phylogenetic group according to phylogenetic analysis based on 16S rRNA gene sequences and specific phenotypic characteristics. Phylogenetic analysis of their 16S rRNA gene sequences revealed that strains KZ01(T), KZ02, KZ03 and GG02 formed a single monophyletic cluster and had a distinct line of descent. Based on sequence similarity of the 16S rRNA gene, Lactobacillus fermentum JCM 1173(T) (96.6%) was the closest neighbour to these novel strains, although it was clear that these strains belonged to a different species. Partial pheS sequences also supported these relationships. DNA DNA relatedness between strain KZ01(T) and L. fermentum JCM 1173(T) was less than 22% and the DNA G+C content of strain KZ01(T) was 50.7 mol%. The cell-wall peptidoglycan type was AO (L-Orn D-Asp) and the major fatty acids were C-16:0, C-18:1 omega 9c and C-19:1 cyclo 9,10. Therefore, based on phylogenetic, phenotypic and physiological evidence, these strains represent a novel species of the genus Lactobacillus, for which the name Lactobacillus gorillae sp. nov. is proposed. The type strain is KZ01(T) (=JCM 19575(T)=DSM 28356(T)).