A novel strain, designated SJP7(T), was isolated from sediment of the Tofua Arc of the Tonga Trench. The 16S rRNA gene sequence of the isolate showed the highest similarity to that of Marinoscillum pacificum KCCM 42325(T) (95.9%). Phylogenetic analysis revealed that the isolate formed a distinct phyletic line with Marinoscillum pacificum KCCM 42325(T) and Marinoscillum furvescens LMG 13023(T) within the family Cytophagaceae. Cells of strain SJP7(T) were Gram-stain-negative and appeared as long rods that were motile by gliding. Growth was observed at 15-40 °C (optimum, 30 °C), at pH 5.5-9.0 (optimum, pH 7.5-8.0) and in the presence of 0.5-7.0% (w/v) NaCl (optimum, 2.5-3%). The major respiratory quinone was MK-7. The dominant fatty acids were summed feature 3 (comprising C(16:1)ω7c and/or C(16:1)ω6c), iso-C(15:0) and C(16:1)ω5c. The DNA G+C content was 43.5 mol%. These properties support the affiliation of strain SJP7(T) with the genus Marinoscillum. Further phenotypic differentiation of strain SJP7(T) from other species of the genus Marinoscillum was indicated by the results of physiological and biochemical tests. On the basis of evidence from our polyphasic taxonomic study, strain SJP7(T) represents a novel species of the genus Marinoscillum, for which the name Marinoscillum luteum sp. nov. is proposed. The type strain of Marinoscillum luteum is SJP7(T) ( =KCTC 23939(T) =NCAIM B02491(T)).