A Gram-negative, aerobic, neutrophilic, moderately halophilic bacterial strain, HS225(T), was isolated from seawater samples around the Zhoushan Archipelago, Zhejiang Province, China. The isolate grew optimally in media with 5.0 % NaCl, at pH 7.0-8.0 and at 25-30 degrees C. The predominant fatty acids were C(16 : 0)omega9c, C(16 : 0), C(12 : 0) 3-OH and C(18 : 1)omega9c. The genomic DNA G+C content was 59.0 mol%. Based on 16S rRNA gene sequence analysis, the isolate was found to be affiliated to the genus Marinobacter. Strain HS225(T) exhibited closest phylogenetic affinity to Marinobacter koreensis DD-M3(T) (98.1 % 16S rRNA gene sequence similarity). DNA-DNA relatedness data and DNA G+C contents as well as physiological and biochemical test results allowed the genotypic and phenotypic differentiation of strain HS225(T) from closely related species. Therefore, it is proposed that strain HS225(T) represents a novel species of the genus Marinobacter, for which the name Marinobacter pelagius sp. nov. is proposed. The type strain is HS225(T) (=CGMCC 1.6775(T) =JCM 14804(T)).