A Gram-stain-negative, strictly aerobic, non-motile, rod-shaped, manganese-oxidizing bacterial strain, designated DY6-4T, was isolated from the surface sediment of the Pacific Clarion-Clipperton Fracture Zone. Phylogenetic analysis, based on 16S rRNA gene sequences, indicated that strain DY6-4T formed a lineage within the family Rhodobacteraceae and was distinct from the most closely related genera Sulfitobacter, Aliiroseovarius and Loktanella (94.0-96.0 %, 93.4-96.0 % and 91.9-95.9 % 16S rRNA gene sequence similarity, repectively). Optimal growth occurred in the presence of 1 % (w/v) NaCl, at pH 7.0 and at 28 °C. Strain DY6-4T contained ubiquinone-10 (Q-10) as the major ubiquinone, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine and one unidentified aminolipid as the predominant polar lipids, C18 : 1ω7c and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) as the main fatty acids (>10 % of the total). The DNA G+C content of strain DY6-4T was 66.6 mol%. On the basis of the polyphasic analyses, strain DY6-4T is considered to represent a novel species of a novel genus in the Roseobacter clade of the family Rhodobacteraceae, for which the name Xuhuaishuia manganoxidans gen. nov., sp. nov. is proposed. The type strain is DY6-4T ( = KCTC 42421T = MCCC 1K00502T).