Cloacimonas fortuita was co-isolated from an enrichment culture of a methanogenic reactor containing anaerobic wastewater sludge, alongside its archaeal syntrophic partner Methanothrix and other minor bacterial species. The genome of this species is 1.98 Mb in length, with a GC content of 36.6%, and encodes 1591 genes, including 1529 protein-coding genes. Based on the functional annotation, it is presumed to perform syntrophic propionate oxidation via an alternative pathway. Genome of this species and its relative C. acidaminovorans have an Average Nucleotide Identity of 78.3%, which is below the species-level cut-off (95%) but above the genus-level threshold (>70%). Therefore, we would like to claim a new species within the known Cloacimonas genus.