Two Gram-reaction-negative, rod-shaped, non-motile and red-pink-pigmented bacterial strains, designated GYR3077(T) and GSR0100(T), were isolated from a water sample of the Mangyung estuary enclosed by the Saemangeum Embankment in JEOLlabuk-do, South Korea, and were characterized using a polyphasic approach. 16S rRNA genes of strains GYR3077(T) and GSR0100(T) exhibited sequence similarities of 95.9 % to Hymenobacter deserti ZLB-3(T) and 96.6 % to Hymenobacter soli PB17(T), respectively, and indicated that these isolates belonged to the phylum Bacteroidetes. The major cellular fatty acids present in the two isolates were iso-C15 : 0, C16 : 1ω5c, summed feature 4 (iso-C17 : 1 I and/or anteiso-C17 : 1 B) and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The major respiratory quinone and polyamine patterns were menaquinone-7 and sym-homospermidine, characteristic of the genus Hymenobacter. Flexirubin-type pigments were absent in both strains. The DNA G+C contents of strains GYR3077(T) and GSR0100(T) were 60.2 mol% and 61.9 mol%, respectively. The major polar lipid of strains GYR3077(T) and GSR0100(T) was phosphatidylethanolamine. Based on the morphological and physiological properties, strains GYR3077(T) and GSR0100(T) were considered to represent two novel species of the genus Hymenobacter, for which the names Hymenobacter koreensis sp. nov. (type strain GYR3077(T) = KACC 16451(T) = JCM 17924(T)) and Hymenobacter saemangeumensis sp. nov. (type strain GSR0100(T) = KACC 16452(T) = JCM 17923(T)) are proposed.