A taxonomic study was carried out on a Gram-staining-negative bacterium, strain SF-12T, isolated from an unidentified starfish living in Sanya, PR China. Cells of SF-12T were non-spore-forming rods, 0.5-0.8 µm wide, 2.2-2.5 µm long and motile by means of flagella. SF-12T was facultatively anaerobic, heterotrophic, oxidase- and catalase-positive. Growth of SF-12T occurred at 15-38 °C (optimum, 30 °C), at pH 6.5-8.5 (optimum, pH 7.0), and in the presence of 2.0-7.0 % (w/v) NaCl (optimum, 3.0-4.0 %). The predominant fatty acids of SF-12T were C18 : 1ω7c and/or C18 : 1ω6c. Ubiquinone 10 was the sole respiratory quinone of SF-12T. The major polar lipids of SF-12T were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, three unknown aminolipids, and seven unknown phospholipids. The DNA G+C content was 61 mol%. SF-12T showed the highest 16S rRNA gene sequence similarity to Lutimaribacter pacificus W11-2BT (96.06 %), followed by Cribrihabitans neustonicus CC-AMHB-3T (96.02 %), Lutimaribacter saemankumensis SMK-117T (96.0 %), Cribrihabitans marinus CZ-AM5T (95.92 %), Lutimaribacter litoralis KU5D5T (95.92 %) and other species of the family Rhodobacteraceae(<95.9 %). However, phylogenetic trees based on 16S rRNA gene sequences showed that SF-12T formed a lineage with members of the genus Lutimaribacter in the trees. On the basis of phenotypic, chemotaxonomic and phylogenetic analyses, SF-12T is considered to represent a novel species of the genus Lutimaribacter, for which the name Lutimaribacter marinistellae sp. nov. is proposed. The type strain is SF-12T (=MCCC 1K01154T=KCTC 42911T).