A Gram-stain-negative, aerobic, rod-shaped, non-motile and pink-pigmented bacterial strain, designated 16F7GT, was isolated from river water. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 16F7GT belongs to the genus Hymenobacter. The 16S rRNA gene sequence similarity to members of the genus Hymenobacter ranged from 90.5 to 97.4 %, and the most closely related strains were Hymenobacter rigui WPCB131T (97.4 %) and Hymenobacter xinjiangensis X2-1gT (97.3 %). Strain 16F7GT had <70 % DNA-DNA relatedness with H. rigui (32.8±7.8 %) and H. xinjiangensis (30.2±6.2 %), indicating that it represents a novel genospecies. Cells were catalase- and oxidase-positive. The genomic DNA G+C content was 56.6 mol%. The major fatty acids were summed feature 4 (C17 : 1iso I/C17 : 1 anteiso B; 19.8 %), summed feature 3 (C16 : 1ω7c/C16 : 1ω6c; 18.4 %), C15 : 0 iso (17.0 %), C16 : 1ω5c (11.8 %) and C15 : 0 anteiso (9.8 %). The major polar lipid was phosphatidylethanolamine and the predominant respiratory quinone was menaquinone 7 (MK-7). Based on the phylogenetic, phenotypic, genotypic and chemotaxonomic analyses, it is concluded that strain 16F7GT represents a novel species within the genus Hymenobacter, for which the name Hymenobacter seoulensis sp. nov. is proposed. The type strain is 16F7GT (=KCTC 52197T=JCM 31655T).