Two Gram-stain-positive, aerobic, rod-shaped, and motile strains FJAT-53684 T and FJAT-54145 T were isolated from the mangrove sediment. They optimally grew at pH 8.0 and could tolerate NaCl up to 5% (w/v). The optimum temperature for growth of strains FJAT-53684 T and FJAT-54145 T were 35 and 40 ºC, respectively. The 16S rRNA gene sequence similarity between FJAT-53684 T and FJAT-54145 T was 97.1%. Both strains showed the highest 16S rRNA gene sequence similarity to the Cytobacillus species. Menaquinone-7 was the only respiratory quinone present in both strains. The major fatty acids (≥ 10%) in strain FJAT-53684 T were iso-C14:0, anteiso-C15:0, iso-C15:0, and iso-C19:0, while strain FJAT-54145 T consist of iso-C14:0, iso-C15:0, iso-C19:0, iso-C16:0, and C16:1ω7c alcohol. The polar lipids present in both strains were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unidentified lipid, unidentified phospholipid, and phosphatidylinositol. Their average nucleotide identity and digital DNA–DNA hybridization values were below the threshold values (95% and 70%, respectively) for species delineation. Based on the above results, strains FJAT-53684 T and FJAT-54145 T represent two novel species of the genus Cytobacillus, for which the names Cytobacillus mangrovibacter sp. nov., and Cytobacillus spartinae sp. nov., are proposed. The type strains are FJAT-53684 T (= JCM 35618 T = GDMCC 1.3071 T), and FJAT-54145 T (= JCM 35621 T = GDMCC 1.3079 T).