A novel proteobacterial bacterium, designated strain CAU 1489T, was isolated from Jeju Island, Republic of Korea. Cells were strictly anaerobic, Gram stain-negative, cream-pigmented, non-spore-forming, motile and short rod-shaped. Strain CAU 1489T exhibited the highest 16S rRNA gene sequence similarity (98. 2%) to Nitratireductor mangrovi SY7T. Multilocus sequence analysis of 16S rRNA and four housekeeping genes (rpoB, rpoC, gyrB and dnaK) indicated that CAU 1489T represents a distinct branch within Nitratireductor. The whole genome was 4.8 Mb with a G + C content of 64.7 mol%, including protein-coding genes related to the function terms amino acids and derivatives, nucleotides and nucleosides, protein metabolism, carbohydrates and cofactors, vitamins, prosthetic groups and pigments. The major fatty acids were 11-methyl C18:1ω7c, cyclo- C19:0ω8c, iso-C17:0 and summed feature 8 (C18:1ω6c and/or C18:1ω7c), and the predominant respiratory quinone was Q-10. The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and two unidentified phospholipids. Digital DNA-DNA hybridization and average nucleotide identity values were 19.4-22.0% and 72.4-79.1%, respectively. On the basis of taxonomic characterization, strain CAU 1489T constitutes a novel species, for which the name Nitratireductor arenosus sp. nov. is proposed. The type strain is CAU 1489T ( = KCTC 62997T = NBRC 113694T).