Two anaerobic, non-spore-forming, non-motile, Gram-negative-staining bacteria, strains YIT 12060T and YIT 12061T, were isolated from human faeces. Cells of strain YIT 12060T were coccoid to rod-shaped with round ends, positive for catalase, negative for indole and oxidase production, produced succinic and acetic acids as end products of glucose metabolism in peptone/yeast extract/glucose medium and had a DNA G+C content of 55.2 mol%. The main respiratory quinones were MK-10 (40 %) and MK-11 (57 %). Fatty acid analysis demonstrated the presence of a high concentration of iso-C15 : 0 (56 %). Following 16S rRNA gene sequence analysis, this strain was found to be most closely related to species of the genus Alistipes, with 90.9–92.6 % gene sequence similarities to type strains of this species. Phylogenetic analysis and biochemical data supported the affiliation of strain YIT 12060T to the genus Alistipes of the family ‘Rikenellaceae’. Strain YIT 12060T therefore represents a novel species of the genus Alistipes for which the name Alistipes indistinctus sp. nov. is proposed; the type strain is YIT 12060T (=DSM 22520T=JCM 16068T). Cells of the other isolate, strain YIT 12061T, were pleomorphic rods that were asaccharolytic, catalase- and oxidase-negative, positive for gelatin hydrolysis and indole production, produced small amounts of succinic, acetic and iso-valeric acids as end products of metabolism in peptone/yeast extract medium and had a DNA G+C content of approximately 42.4 mol%. On the basis of 16S rRNA gene sequence similarity values, this strain was shown to belong to the family ‘Porphyromonadaceae’ and related to the type strains of Odoribacter splanchnicus (89.6 %) and Odoribacter denticanis (86.2 %); similarity values with strains of recognized species within the family ‘Porphyromonadaceae’ were less than 84 %. Biochemical data supported the affiliation of strain YIT 12061T to the genus Odoribacter. Strain YIT 12061T therefore represents a novel species for which the name Odoribacter laneus sp. nov. is proposed; the type strain is YIT 12061T (=DSM 22474T=JCM 16069T).