A novel species belonging to the genus Grimontia is described in this study. A Gram-negative, chemoheterotrophic, obligately aerobic, catalase- and oxidase-positive, motile by a single polar flagellum, and rod-shaped bacterium, designated $IMCC5001^T$, was isolated from surface seawater of the Yellow Sea. Strain $IMCC5001^T$ grew optimally at $30^{circ}C$ in the presence of 3.5% NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate was related most closely to Grimontia hollisae with a sequence similarity of 95.8%, and formed a robust phyletic lineage with Grimontia hollisae. Differential physiological characteristics between the new strain and Grimontia hollisae KCCM $41680^T$ and chemotaxonomic characterization including determination of DNA G+C content, fatty acid methyl esters, quinone composition, and polar lipid profiles justified the assignment of strain $IMCC5001^T$ to the genus Grimontia as a novel species. In conclusion, strain $IMCC5001^T$ represents a new species, for which the name Grimontia marina sp. nov. is proposed, with the type strain $IMCC5001^T$ (=KCTC $22666^T$ =NBRC $105794^T$).