A motile, rod-shaped, pale-brown-pigmented bacterium, designated strain C4T, was isolated from seawater collected from the South Sea (Republic of Korea). Cells were Gram-negative, facultatively anaerobic, and catalase- and oxidase-positive. The major fatty acids were summed feature 3 (C16:1omega7c and/or iso-C15:0 2-OH; 19.4%), C16:0 (16.3%), C17:1omega8c (9.5%) and iso-C15:0 (7.7%). The DNA G+C content was 40.8 mol%. A phylogenetic tree based on 16S rRNA gene sequences showed that strain C4T formed a lineage within the genus Shewanella (92.7-96.1% sequence similarity to representative strains of the genus Shewanella) and was part of a distinct branch with the clade comprising Shewanella haliotis DW01T and Shewanella algae ATCC 51192T. Phenotypic characteristics enabled strain C4T to be distinguished from S. haliotis and S. algae. On the basis of the data presented in this study, strain C4T represents a novel species, for which the name Shewanella marina sp. nov. is proposed. The type strain is C4T (=KCTC 22185T=JCM 15074T).