A Gram-stain-negative, coccoid to oval-shaped and non-motile bacterial strain, designated MM-7T, was isolated from seawater of the Yellow Sea, South Korea, and was subjected to a polyphasic taxonomic study. Strain MM-7T grew optimally at pH 7.0-8.0, at 25 °C and in the presence of 2-3 % (w/v) NaCl. A neighbour-joining phylogenetic tree based on 16S rRNA gene sequences showed that strain MM-7T joins the branch comprising the species of the genus Roseobacter, clustering with the type strains of Roseobacter litoralis and Roseobacter denitrificans, with which it exhibited 97.9 and 96.8 % sequence similarity values, respectively. The DNA G+C content of strain MM-7T was determined to be 60.8 mol%, and its mean DNA-DNA relatedness values with Rsb. litoralis JCM 21268T was 10.3±0.4 %. Strain MM-7T contained Q-10 as the predominant ubiquinone and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) as the major fatty acid. The major polar lipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylglycerol, an unidentified aminolipid and an unidentified lipid. Differential phenotypic properties, together with the phylogenetic distinctiveness, demonstrated that strain MM-7T is distinguishable from other species of the genus Roseobacter. On the basis of the data presented, strain MM-7T is considered to represent a novel species of the genus Roseobacter, for which the name Roseobacter ponti sp. nov. is proposed. The type strain is MM-7T (=KCTC 52469T=NBRC 112431T).