A novel Gram-stain-negative bacterium, named strain NSCS20N07DT, was isolated from surface seawater of the South China Sea. Cells of this strain contained poly-β-hydroxybutyrate granules. Growth was observed at 15-35 °C with optimum of 30 °C, at a salinity range of 1-6 % (w/v) NaCl with optimum of 3 % and at pH 5-8 with optimum of pH 5. The full-length 16S rRNA gene sequence of strain NSCS20N07DT showed highest similarity to Photobacterium iliopiscarium ATCC 51760T of 96.0 %, followed by Photobacterium kishitanii pjapo.1.1T, Photobacterium phosphoreum ATCC 11040T and Photobacterium aquimaris LC2-065T of 96.0, 95.8 and 95.7 %, respectively. Phylogenetic analysis showed that strain NSCS20N07DT formed a separate clade distinct from species of the genus Photobacterium and other genera within the family Vibrionaceae, indicating that strain NSCS20N07DT represented a novel genus affiliated with this family. The genome size of strain NSCS20N07DT was 2.5 Mb, which was much smaller than those of related species in the family Vibrionaceae. The predominant fatty acids were C16 : 0, C17 : 0 cyclo, C19 : 0 cyclo ω8c, C18 : 0 and summed feature 2 (C14 : 0 3-OH/iso-C16 : 1 I). The respiratory quinone was Q-8. The polar lipids were identified as phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and four unidentified lipids. The DNA G+C content was 30.7 mol%. Combined, these results suggest that strain NSCS20N07DT represents a novel species of a new genus, for which the name Paraphotobacterium marinum gen. nov., sp. nov. is proposed. The type strain of Paraphotobacterium marinum is NSCS20N07DT (=KCTC 52126T=MCCC 1A01886T=CIP 111031T).