A Gram-stain-negative, aerobic, oxidase- and catalase-positive, flagellated, rod-shaped bacterial strain, designated SM1222(T), was isolated from the deep-sea sediment of the South China Sea. The strain grew at 4-35 °C and with 0.5-8 % NaCl (w/v). Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain SM1222(T) was affiliated with the genus Oceanisphaera in the class Gammaproteobacteria. It shared the highest sequence similarity with the type strain of Oceanisphaera ostreae (96.8 %) and 95.4-96.6 % sequence similarities with type strains of other species of the genus Oceanisphaera with validly published names. Strain SM1222(T) contained summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH), C18 : 1ω7c, C16 : 0, C12 : 0 and summed feature 2 (C14 : 0 3-OH and/or iso-C16 : 1 I) as the major fatty acids and ubiquinone Q-8 as the predominant respiratory quinone. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The genomic DNA G+C content of strain SM1222(T) was 51.5 mol%. On the basis of the evidence presented in this study, strain SM1222(T) represents a novel species of the genus Oceanisphaera, for which the name Oceanisphaera profunda sp. nov. is proposed. The type strain of Oceanisphaera profunda is SM1222(T) ( = CCTCC AB 2013241(T) = KCTC 32510(T)). An emended description of the genus Oceanisphaera Romanenko et al. 2003 emend. Choi et al. 2011 is also proposed.