A strictly anaerobic Gram-stain-positive, non-motile and non-spore-forming bacterial strain, BR31T, was isolated from a faecal sample of a healthy human. Bacterial colonies were ivory-coloured on GAM agar and composed of rod-shaped cells with rounded ends approximately 1.4-2.1×0.5-0.6 µm in size. According to comparative analysis based on 16S rRNA gene sequences, strain BR31T formed a distinct phylogenetic lineage that reflects a new genus within Clostridium cluster XIVa in the family Lachnospiraceae, with highest similarity to Eubacterium contortum DSM 3982T (94.6 %). The DNA G+C content was calculated to be 47.0 mol% from whole genome sequencing. Predicted genes associated with synthesis of teichuronic acid, polyamines, polar lipids and diaminopimelic acid were detected. The peptidoglycan contained meso-diaminopimelic acid and the main polar lipid detected was phosphatidylglycerol. The major metabolic end product of glucose was acetic acid, which was in agreement with those of most members of the family. However, the profile of major cellular fatty acids (C16 : 0, C14 : 0, summed feature 4 and C13 : 0) and overall enzyme activity demonstrated phenotypic differentiation of strain BR31T from other closely related genera. Thus, based on distinct phenotypic, phylogenetic, genotypic and chemotaxonomic characteristics, strain BR31T is considered to represent a novel species of a new genus, for which the name Merdimonas faecis gen. nov., sp. nov. is proposed. The type strain of Merdimonas faecis is BR31T (=KCTC 15482T=JCM 30748T).