Three Gram-negative, aerobic, motile, halophilic, rod-shaped strains (CN46(T), CN71 and CN74(T)) were isolated from sediment of the East China Sea and subjected to a polyphasic taxonomic study. Strains CN46(T) and CN71 had identical 16S rRNA gene sequences and phenotypic characteristics. Strain CN46(T) was moderately halophilic. Growth of strain CN46(T) was observed between 0.5 and 10.0 % (w/v) NaCl (optimal growth at 3.0-5.0 %) and between pH 6.5 and 9.0. Strain CN74(T) grew over a wider range of pH (pH 6.0-9.5); the optimum NaCl concentration for growth was 1.0-3.0 %. The major fatty acids of strain CN46(T) were C(16 : 1)omega9c, C(16 : 0) and C(12 : 0), whereas strain CN74(T) contained C(16 : 0), C(16 : 1)omega9c, C(18 : 1)omega9c and C(12 : 0). The DNA G+C contents of the three isolates were between 58.0 and 58.9 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strains CN46(T), CN71 and CN74(T) grouped together within the cluster of Marinobacter species. 16S rRNA gene sequence similarities of the three strains with the type strains of Marinobacter species ranged from 94.0 to 97.1 %. The DNA-DNA hybridization values of strain CN74(T) with strains CN46(T) and CN71 were 35.0 and 36.0 %, respectively. Levels of DNA-DNA relatedness between strains CN46(T) and CN74(T) and Marinobacter pelagius CGMCC 1.6775(T), Marinobacter gudaonensis CGMCC 1.6294(T) and Marinobacter koreensis DSM 17924(T) were 15.3-45.2 %. The results of DNA-DNA hybridizations, fatty acid analysis, and physiological and biochemical tests allowed genotypic and phenotypic differentiation of the isolates from closely related species. Two novel species are proposed, named Marinobacter mobilis sp. nov. (type strain CN46(T) =CGMCC 1.7059(T) =JCM 15154(T)) and Marinobacter zhejiangensis sp. nov. (type strain CN74(T) =CGMCC 1.7061(T) =JCM 15156(T)).