A Gram-stain-negative, non-motile, ovoid or rod-shaped bacterial strain, designated L-6(T), was isolated from seawater of Baekdo harbour of the East Sea in Korea and its taxonomic position was investigated by using a polyphasic study. Strain L-6(T) grew optimally at 30 �XC, at pH 7.5-8.0 and in the presence of 2 % (w/v) NaCl. In the neighbour-joining phylogenetic tree based on 16S rRNA gene sequences, strain L-6(T) formed a cluster with the type strain of Celeribacter neptunius at a bootstrap resampling value of 100 %. Strain L-6(T) exhibited 16S rRNA gene sequence similarity values of 97.7 % to C. neptunius H 14(T) and of less than 96.2 % to the type strains of other species used in the phylogenetic analysis. The G+C content of the chromosomal DNA of strain L-6(T) was 60.9 mol%. The predominant ubiquinone found in strain L-6(T) and C. neptunius CIP 109922(T) was ubiquinone-10 (Q-10). The predominant fatty acid of strain L-6(T) and C. neptunius CIP 109922(T) was C(18:1)�s7c. The major polar lipids of strain L-6(T) were phosphatidylglycerol, one unidentified aminolipid and one unidentified lipid. The mean level of DNA-DNA relatedness between strain L-6(T) and C. neptunius CIP 109922(T) was 17 %. Differential phenotypic properties, together with phylogenetic and genetic distinctiveness, demonstrated that strain L-6(T) is distinguishable from C. neptunius. On the basis of the data presented, strain L-6(T) is considered to represent a novel species of the genus Celeribacter, for which the name Celeribacter baekdonensis sp. nov. is proposed. The type strain is L-6(T) (= KCTC 23497(T) = CCUG 60799(T)).