A gram-staining-negative, strictly aerobic, rod shaped, and motile bacterium with a single polar flagellum, designated H26(T), was isolated from tidal flat sediment in Jeju Island, South Korea. Growth of strain H26T was observed at 4-35 degrees C (optimum, 20-25 degrees C), pH 6.0-9.0 (optimum, pH 7.0-8.0), and 1-4 % NaCl (optimum, 2-3 %). Phylogenetic analyses based on 16S rRNA gene sequences showed that strain H26(T) formed a phyletic lineage within the genus Rheinheitnera, family Chrotnatiaceae. Strain H26(T) was most closely related to Rheinheimera baltica OSBAC1(T), Rheinheimera aestuarii H29(T), Rheinheimera tnuenzenbergensis E49(T), and Rheinheimera aquimaris SW-353(T) with 98.5, 98.1, 97.8, and 97.5 % of 16S rRNA gene sequence similarities, respectively. The DNA DNA relatedness levels between strain H26(T) and the type strains of R. baltica, R. aestuarii, R. tnuenzenbergensis, and R. aquimaris were 35.5 +/- 3.2, 33.4 +/- 1.5, 31.2 +/- 2.2, and 28.7 +/- 0.9 %, respectively. The major fatty acids of strain H26T were iso-C-15:0 3-OH, summed feature 3 (comprising H26(T) omega 7c/C-16:1 omega 6c), C-16:0, summed feature 8 (comprising C-18.1 omega 7c/C-18 :1 omega 6C), iSo-C-17:0 0 3-OH, and C-12:0 3-OH and the strain contained ubiquinone (Q-8) as the sole isoprenoid quinone. Phosphatidylethanolamine, phosphatidylglycerol, and an aminolipid were identified as the major polar lipids and the G + C content of the genomic DNA was 52.0 mol%. Based on the phenotypic, chemotaxonomic, and molecular properties, strain H26(T) represents a novel species of the genus Rheinheimera, for which the name Rheinheimera gaetbuli sp. nov. is proposed. The type strain was H26(T) (=KACC 18254(T) = JCM 30403(T)).