A novel bacterium designated SSM4.2(T)was isolated from seaweed of Gouqi Island, which is the center of the Zhoushan fishing ground in the East China Sea. Strain SSM4.2(T)was Gram-stain-negative, bright yellow-pigmented, short rod-shaped, non-flagellated, non-spore forming, aerobic and motile by gliding. Growth was observed at 4-37 degrees C (optimum 25-30 degrees C), pH 6.0-8.0 (optimum pH 7.0) and 0-2.0% (w/v) NaCl (optimum 0%) concentration. The strain was catalase- and oxidase-positive. Menaquinone-6 (MK-6) was found as the sole respiratory quinone and zeaxanthin as the main carotenoid pigment. The predominant fatty acids (>= 10%) were iso-C-15:0, iso-C(15:1)G, iso-C(17:0)3-OH and summed feature 3 (C-16:1 omega 7c/C-16:1 omega 6c). The major polar lipid was phosphatidylethanolamine (PE). The genome size was 5.7 Mbp. The DNA G + C content was 34.1 mol%. 16S rRNA gene sequence revealed that strain SSM4.2(T)belongs to the genusFlavobacteriumand shares high-sequence similarity withF. limiKACC 18851(T)(98.1%),F. hydrophilumKACC 19591(T)(97.6%),F. defluviiKCTC 12612(T)(97.1%),F. cheongpyeongenseKACC 19592(T)(97.0%) andF. fluviatileKCTC 52446(T)(96.9%). Strain SSM4.2(T)had 73.2-84.6% average nucleotide identity and 19.1-29.4% digital DNA-DNA hybridization values with its closest type strains. Based on its phenotypic, chemotaxonomic, phylogenetic and genomic features, strain SSM4.2(T)represents a novel species of the genusFlavobacterium,for which the nameFlavobacterium ajaziisp. nov. is proposed. The type strain is SSM4.2(T)(= KCTC 72807(T) = MCCC 1K04370(T)).