A Gram-positive bacterium, designated SCSIO 15042(T), was isolated from a sediment of the South China Sea and was subjected to a polyphasic taxonomic study. The isolate grew at 20-60 °C, pH 6.0-10.0 and it could grow with up to 10 % (w/v) NaCl. The cell-wall diamino acid was found to be meso-diaminopimelic acid. Polar lipids were found to be diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine and an unknown polar lipid. The only menaquinone was determined to be MK-7. The major fatty acids were identified as C16:1 ω7c/C16:1 ω6c, C16:0, iso-C15:0, anteiso-C15:0, and iso-C16:0. The DNA G+C content of strain SCSIO 15042(T) was determined to be 43.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences affiliated strain SCSIO 15042(T) to the genus Bacillus. Levels of 16S rRNA gene sequence similarities between strain SCSIO 15042(T) and Bacillus herbersteinensis D-1-5a(T), Bacillus infantis SMC 4352-1(T), Bacillus novalis LMG 21837(T) and Bacillus drentensis LMG 21831(T) were 96.2, 96.2, 96.1 and 96.1 %, respectively. Based on the evidence of the present polyphasic study, strain SCSIO 15042(T) is considered to represent a novel species of the genus Bacillus, for which the name Bacillus abyssalis sp. nov. is proposed. The type strain is SCSIO 15042(T) (=DSM 25875(T) = CCTCC AB 2012074(T) = NBRC 109102(T)).