Two luminous marine bacterial strains, LC2-005(T) and LC2-102, were isolated from seawater at Kuroshio Region and Sagami Bay in Japan, respectively. These bacteria were Gram-negative, oxidase-positive, catalase-positive, motile and rod-shaped. On the basis of 16S rRNA gene sequence analysis, strains LC2-005(T) and LC2-102 formed a cluster within the Vibrio harveyi species group. However, multilocus sequence analysis using five loci (pyrH, ftsZ, mreB, gyrB and gapA) and DNA-DNA hybridization experiments indicated that these strains were distinct from the currently known Vibrio species. Additionally, these strains differ from related Vibrio species in utilization of glucose, mannitol, inositol, sorbitol, rhamnose, sucrose, melibiose and arabinose, production of lysine decarboxylase, ornithine decarboxylase, tryptophan deaminase, esterase (C4), lipase (C4), chymotrypsin, acid phosphatase, alpha-glucosidase, beta-glucosidase and N-acetyl-beta-glucosaminidase and the ability to reduce nitrate to nitrite. The major fatty acids were C(15 : 0) iso 2-OH and/or C(16 : 1)omega7c, C(16 : 0), C(18 : 1)omega7c and C(14 : 0). The DNA G+C contents of strains LC2-005(T) and LC2-102 were 45.2 and 45.5 mol%, respectively. On the basis of the polyphasic taxonomic evidence presented in this study, it can be concluded that strains LC2-005(T) and LC2-102 belong to the same genospecies and represent a novel species of the genus Vibrio, for which the name Vibrio azureus sp. nov. is proposed. The type strain is LC2-005(T) (=NBRC 104587(T) =KCTC 22352(T)).