Two bacterial strains, designated JS4-4(T) and SHS5-24(T), were isolated from forest soil of Jeju Island and fresh water of Seoho lake in Suwon city, respectively, South Korea. Both strains were Gram-stain-negative, aerobic, motile rods. Strains JS4-4(T) and SHS5-24(T) showed high sequence similarities (97.6-95.8 %) and (96.5-95.6 %), respectively, to the members of the genus Undibacterium. The sequence similarity between strains JS4-4(T) and SHS5-24(T) was 97.0 %. A phylogenetic tree showed that these strains fell within the radius of the genus Undibacterium. The main fatty acids of strains JS4-4(T) and SHS5-24(T) were summed feature 3 (C16 : 1�s7c and/or C16 : 1�s6c) (50.1 and 58.7 %, respectively) and C16 : 0 (28.3 and 24.5 %, respectively). Both strains had ubiquinone 8 as the only respiratory quinone, and phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol as the major polar lipids. Strain JS4-4(T) showed <70 % DNA-DNA hybridization with members of the genus Undibacterium. Thus, based on the evidence of a polyphasic study, it is proposed that strains JS4-4(T) and SHS5-24(T) represent two novel species, for which the names Undibacterium jejuense sp. nov. (type strain JS4-4(T) = KACC 12607(T) = NBRC 108922(T)) and Undibacterium seohonense sp. nov. (type strain SHS5-24(T) = KACC 16656(T) = NBRC 108929(T)) are proposed.