A Gram-stain-negative, aerobic, non-motile, non-spore-forming, rod-shaped bacterial strain, designated CAU 1304, was isolated from sea sand. Strain CAU 1304 grew optimally at pH 8.5 and 30 °C and in the presence of 1 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain CAU 1304 belonged to the family Rhodobacteraceae, and was most closely related to Roseicitreum antarcticum ZS2-28 (96.54 % similarity) and Rhodobacter veldkampii ATCC 35703 (96.46 %). The major fatty acid was C18 : 1ω7c and the respiratory quinone was Q-10. The polar lipids were composed of phosphatidylglycerol, phosphatidylcholine and an unidentified aminolipid. The DNA G+C content was 55.9 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic analysis, it is proposed that strain CAU 1304 represents a novel species of a new genus of the family Rhodobacteraceae, for which the name Arenibacillus arenosus gen. nov., sp. nov. is proposed. The type strain of Arenibacillus arenosus is CAU 1304 (=KCTC 42827=NBRC 113022).