Gram-negative strains, motile by a single polar flagellum, non-pigmented and with a curved rod-shaped morphology, designated IMCC1826(T) and IMCC1883, were isolated from a surface seawater sample from the Yellow Sea. The two strains shared 99.9% 16S rRNA gene sequence similarity and showed 92% DNA-DNA relatedness, suggesting that they belonged to the same genomic species. Phylogenetic analysis based on 16S rRNA gene sequences showed that the two isolates were related most closely to the type strain of Thalassolituus oleivorans with a sequence similarity of 96.4% and formed a robust phyletic lineage with T. oleivorans. DNA-DNA relatedness between the two strains and T. oleivorans DSM 14913(T) was 8.7-11.6%. A putative alkane hydroxylase (alkB) gene was detected in strain IMCC1826(T) by PCR, but the amino acid sequence of the gene was distantly related to that of the AlkB homologue of T. oleivorans DSM 14913(T). As expected from the presence of the alkB gene, the new strains utilized n-tetradecane and n-hexadecane as a carbon source. The DNA G+C content was 54.6-56.0 mol% and the main isoprenoid quinone detected was Q-9. Polar lipids of strain IMCC1826(T) included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and amino-group-containing lipids. On the basis of taxonomic data obtained in this study, strains IMCC1826(T) and IMCC1883 represent a novel species of the genus Thalassolituus, for which the name Thalassolituus marinus sp. nov. is proposed, with IMCC1826(T) (=KCTC 23084(T)=NBRC 107590(T)) as the type strain.