A Gram-strain-negative, coccoid bacterium, lacking bacteriochlorophyll, designated strain T11g56(T), was isolated from a sediment sample collected from Ximen island mangrove forest, Zhejiang province, China. Cells were halotolerant, and catalase- and oxidase-positive. Growth was observed at 18-42 degrees C (optimum, 35 degrees C), at pH 6.0-9.5 (optimum, pH 6.5) and in the presence of 0-15 % (w/v) NaCl (optimum, 2-5 %). The major cellular fatty acids were C-18:1 omega 7c and C-1(6:)0 . The polar lipid profile of strain T11g56(T)- consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylmonomethylethanolamine, two unidentified phospholipids and five unidentified lipids. Ubiquinone-10 was the predominant respiratory quinone. The assimilation of the substrates in the API 20NE kit was positive in strain T11g56(T). The DNA G+C content of strain T11g56(T )was 67.2 mol%. 16S rRNA gene sequence analysis indicated that strain T11g56(T) was a member of family Rhodobacteraceae and was closely related to Poseidonocella pacifica KMM 9010(T), with 95.7 % similarity to the type strain. Phylogenetic analysis showed that strain T11g56(T)-formed a separate evolutionary branch, and was parallel to other related genera of Rhodobacteraceae. Its phylogenetic distinctiveness and distinguishing phenotypic characteristics supported that strain T11g56(T)-represents a novel genus of the family Rhodobacteraceae, for which the name Mangrovicoccus ximenensis gen. nov., sp. nov. is proposed. The type strain is T11g56(T) (=CCTCC AB 2016238(T) =KCTC 52623(T)).