A halophilic, Gram-staining-negative, rod-shaped, agellated and motile bacterium, strain QX-1 T , was isolated from deep-sea sediment at a depth of 3332 m in the southwestern Indian Ocean. Strain QX-1 T growth was observed at 4-50 °C (optimum 37 °C), pH 5.0-11.0 (optimum pH 7.0), 3%-25% NaCl (w/v; optimum 7%), and it did not grow without NaCl. A phylogenetic analysis based on the 16S rRNA gene placed strain QX-1 T in the genus Halomonas and most closely related to Halomonas sul daeris (97.90%), Halomonas zhaodongensis (97.80%), Halomonas songnenensis (97.59%), Halomonas hydrothermalis (97.37%), Halomonas subterranea (97.25%), Halomonas salicampi (97.09%), and Halomonas arcis (97.01%). DNA-DNA hybridization (< 26.50%) and average nucleotide identity values (< 83.54%) between strain QX-1 T and the related type strains meet the accepted criteria for a new species. The principal fatty acids (> 10%) of strain QX-1 T are C 16:0 (25.50%), C 17:0 cyclo (14.02%), C 19:0 cyclo ω8c (18.72%), and summed feature 8 (C 18:1 ω7c and/or C 18:1 ω6c, 18.08%). The polar lipids of strain QX-1 T are mainly diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unidenti ed phospholipid, unidenti ed aminophospholipid, and ve unidenti ed lipids. The main respiratory quinone is Q-9. The G+C content of its chromosomal DNA is 54.4 mol%. Its fatty acid pro le, respiratory quinones, and G+C content also support the placement of QX-1 T in the genus Halomonas. These phylogenetic, phenotypic, and chemotaxonomic analyses indicate that QX-1 T is a novel species, for which the name Halomonas maris is proposed. The type strain is QX-1 T (=MCCC 1A17875 T = KCTC 82198 T = NBRC 114670 T ).