Two luminous marine bacteria, strains LC2-065(T) and LC2-102, were isolated from seawater at Sagami Bay in Japan. These bacteria were Gram-negative, oxidase-negative, catalase-positive, motile and coccoid-rods. 16S rRNA gene sequence analysis and multilocus sequence analysis (MLSA) using six loci (ftsZ, gapA, gyrB, mreB, pyrH and topA) and sequence analysis of the alpha subunit of luciferase (luxA) gene revealed that these bacteria were distinct from other species of the genus Photobacterium. These novel strains were most closely related to Photobacterium kishitanii. The DNA-DNA hybridization value between strain LC2-065(T) and Photobacterium kishitanii ATCC BAA-1194(T) was 42.1 %. The major fatty acids were C(12 : 0,) C(14 : 0), C(16 : 0), C(18 : 0) and C(15 : 0) iso 2-OH and/or C(16 : 1)omega7c (summed feature 3). The DNA G+C contents of strains LC2-065(T) and LC2-086 were 42.2 and 42.9 mol%, respectively. The phenotypic features of the novel strains were similar to those of P. kishitanii and P. phosphoreum, but there were sufficient physiological differences for the novel strains to be easily differentiated. On the basis of these results, these new strains represent a novel species, for which the name Photobacterium aquimaris sp. nov. is proposed. The type strain is LC2-065(T) (=NBRC 104633(T)=KCTC 22356(T)).