A Gram-stain-negative, facultatively anaerobic bacterium, designated WM3T, was isolated from surface seawater collected from the East China Sea. Cells were catalase- and oxidase-positive, short rods and motile by means of a single polar flagellum. Growth occurred at 15-43 °C (optimum 37-40 C), pH 5.5-9.5 (optimum pH 6.5-7.5) and with 0.25-9.0 % (w/v) NaCl (optimum 1.0-1.5 %). Chemotaxonomic analysis showed that the respiratory quinone was ubiquinone-8, the major fatty acids included C16 : 0 (23.6 %), C18 : 1ω7c (26.2 %) and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH, 22.1 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain WM3T was most closely related to the genus Marinobacterium, sharing the highest 16S rRNA gene sequence similarity of 95.5 % with both Marinobacterium litorale KCTC 12756T and Marinobacterium mangrovicola DSM 27697T. The genomic DNA G+C content of the strain WM3T was 55.8 mol%. On the basis of phenotypic, chemotaxonomic and genotypic characteristics presented in this study, strain WM3T is suggested to represent a novel species of the genus Marinobacterium, for which the name Marinobacterium zhoushanense sp. nov. is proposed. The type strain is WM3T (=KCTC 42782T=CGMCC 1.15341T).