Culture-based study of the faecal microbiome in two adult female subjects revealed the presence of two obligately anaerobic, non-spore-forming, rod-shaped, non-motile, Gram-negative bacterial strains that represent novel species. The first strain, designated 627^T, was a fastidious, slow-growing, indole-positive bacterium with a non-fermentative type of metabolism. The strain was characterized by the production of acetic and succinic acids as metabolic end products, the prevalence of iso-C_{15 : 0}fatty acid and the presence of menaquinones MK-10 and MK-11. The DNA G+C content was found to be 56.6 mol%. The second strain, designated 177^T, was capable of fermenting a rich collection of carbohydrate substrates, producing acetic acid as a terminal product. The strain was indole-negative and resistant to bile. The major cellular fatty acids were iso-C_{15 : 0}and anteiso-C_{15 : 0}(in a 1 : 1 ratio) and the predominant menaquinone was MK-11. The DNA G+C content was 37.8 mol%. A phylogenomic analysis of the draft genomes of strains 627^Tand 177^Tplaced these bacteria in the generaAlistipes(familyRikenellaceae) andCoprobacter(familyPorphyromonadaceae), respectively.On the basis of the phenotypic and genotypic properties of strains 627^Tand 177^T, we conclude that these strains from human faeces represent two novel bacterial species, for which the namesAlistipes inopssp. nov. (type strain 627^T = DSM 28863^T = VKM B-2859^T) andCoprobacter secundussp. nov. (type strain 177^T = DSM 28864^T = VKM B-2857^T) are proposed.