A coccoid and amorphous-shaped, non-gliding, proteorhodopsin-containing, yellow bacterium, designated strain SG-18(T), was isolated from seawater in the western North Pacific Ocean near Japan. The strain was Gram-stain-negative, obligately aerobic, heterotrophic and oxidase-positive. It hydrolysed aesculin but not DNA, urea, gelatin or agar. Growth occurred in the presence of 1-5 % NaCl, with optimum growth at 2 % NaCl. The strain grew at 15-37 °C with an optimum temperature of 25-30 °C. The DNA G+C content of the genomic DNA of strain SG-18(T) was 47.0 mol% (HPLC). The predominant isoprenoid quinone was MK-6, and major cellular fatty acids were iso-C15 : 1 G, iso-C15 : 0, iso-C15 : 0 3-OH. Phylogenetic trees generated by using 16S rRNA gene sequences revealed that strain SG-18(T) belonged to the family Flavobacteriaceae and showed 92.7 % sequence similarity to the most closely related species, Croceitalea eckloniae DOKDO 025(T). On the basis of phenotypic and phylogenetic features, strain SG-18(T) is classified as representing a novel species of a new genus within the family Flavobacteriaceae, for which the name Aureicoccus marinus gen. nov., sp. nov. is proposed. The type strain of the type species is SG-18(T) ( = NBRC 108814(T) = KCTC 23967(T)).