Strain C5-48T, an anaerobic intestinal bacterium that potentially accumulates acetaldehyde at levels exceeding its minimum mutagenic concentration (50 µM) in the colon and rectum, was isolated from the feces of a patient with alcoholism. The 16S rRNA gene sequence of strain C5-48T showed high similarity to the corresponding sequences of Lachnoclostridium edouardi Marseille-P3397T (95.7%) and Clostridium fessum SNUG30386T (94.7%). However, phylogenetic analysis using the sequences of the 16S rRNA, rpoB, and hsp60 genes and whole-genome analysis strongly suggested that C5-48T should be included in the genus Enterocloster. The novelty of strain C5-48T was further confirmed by comprehensive average nucleotide identity (ANI) calculations based on its whole-genome sequence, which showed appreciable ANI values with known Enterocloster species (e.g., 74.3% and 73.4% with Enterocloster bolteae WAL 16351T and Enterocloster clostridioformis ATCC 25537T, respectively). The temperature range for growth of strain C5-48T was 15–37 °C with an optimum of 37 °C. The pH range for growth was 5.5–10.5 with an optimum of 7.5. The major constituents of the cell membrane lipids of strain C5-48T were 16:0, 14:0, and 18:1 ω7c dimethyl acetal fatty acids. On the basis of the genotypic and phenotypic properties, Enterocloster alcoholdehydrogenati sp. nov. is proposed, with the type strain C5-48T (= JCM 33305T = DSM 109474T).