A Gram-stain-positive endophytic bacterium, designated strain YC6957(T), was isolated from surface-sterilized roots of a halophyte (Elymus mollis Trin.) inhabiting coastal tidal flats of Namhae Island, located on the southern coast of Korea, and was subjected to a polyphasic taxonomic study. Cells were facultatively anaerobic, endospore-forming rods to coccoid rods, motile by a single flagellum. Strain YC6957(T) was catalase-positive, oxidase-negative and able to grow in the presence of 0-8 % (w/v) NaCl, with optimum growth at 4-5 % (w/v) NaCl. Growth occurred at 15-45 °C (optimal growth at 30-35 °C) and pH 6.0-8.5 (optimal growth at pH 7.0-8.0). The predominant isoprenoid quinone was menaquinone 7 (MK-7). The major cellular fatty acids were C(16 : 0) (11.3 %), iso-C(15 : 0) (19.2 %) and anteiso-C(15 : 0) (36.4 %). The cell-wall peptidoglycan contained meso-diaminopimelic acid. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The DNA G+C content was 41.6 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the isolate belonged to the genus Bacillus. Strain YC6957(T) exhibited high 16S rRNA gene sequence similarity to its closest neighbours, Bacillus ruris LMG 22866(T) (96.14 %), Bacillus lentus NCIMB 8773(T) (95.97 %) and Bacillus galactosidilyticus LMG 17892(T) (95.91 %), and less than 95.84 % similarity to all other type strains in the genus Bacillus. On the basis of the phylogenetic, physiological and biochemical data, it is suggested that strain YC6957(T) represents a novel species of the genus Bacillus, for which the name Bacillus graminis sp. nov. is proposed. The type strain is YC6957(T) ( = KACC 13779(T) = DSM 22162(T)).