A Gram-positive, moderately halophilic, moderately thermophilic, endospore-forming, catalase- and oxidase-positive, obligately aerobic bacterium, strain YIM-C55.5(T), was isolated from saline soil in the Qaidam Basin, north-west China. Cells were slender rods, motile by means of peritrichous flagella. Filamentous forms were present throughout the growth cycle. Strain YIM-C55.5(T) was able to grow in the presence of 7-30 % (w/v) NaCl and at pH 6.0-9.0, with optimum growth at 15 % (w/v) NaCl and pH 7.0. It was able to grow at 28-60 degrees C, with optimum growth at 45-50 degrees C. meso-Diaminopimelic acid was present in the cell-wall peptidoglycan. The major cellular fatty acids were iso-C(15 : 0), C(16 : 0), anteiso-C(15 : 0), anteiso-C(17 : 0) and C(18 : 0). Strain YIM-C55.5(T) possessed menaquinone 7 (MK-7) as the predominant respiratory quinone and diphosphatidylglycerol and phosphatidylglycerol as polar lipids. The genomic DNA G+C content was 42.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain YIM-C55.5(T) belonged to the family Bacillaceae and was related most closely to members of the genus Gracilibacillus, but with low levels of similarity to the type strains of recognized species of the genus (Gracilibacillus orientalis XH-63(T), 95.1 %; Gracilibacillus boraciitolerans T-16X(T), 94.0 %; Gracilibacillus dipsosauri DD1(T), 93.7 %; Gracilibacillus halotolerans NN(T), 93.5 %). Together with phenotypic data, these results suggest that strain YIM-C55.5(T) represents a novel species of the genus Gracilibacillus, for which the name Gracilibacillus halophilus sp. nov. is proposed. The type strain is YIM-C55.5(T) (=DSM 17856(T) =CGMCC 1.6303(T)).