A novel marine bacterium, designated 04OKA-3-218T, was isolated from the hard coral Galaxea fascicularis L. collected in Japan. The strain was dark-brown-pigmented, Gram-negative, strictly aerobic, curved-rod-shaped and non-motile. Phylogenetic analysis based on the 16S rRNA gene sequence showed the affiliation of the isolate with members of the family Flavobacteriaceae of the phylum Bacteroidetes, with the highest sequence similarity (95.2%) to Spongiibacterium pacificum SW169T. The DNA G+C content was 42.9 mol%; MK-6 was the major menaquinone; with iso-C17:0 3-OH (28.8%), iso-C15:0 (26.8%) and iso-C15:1 H and/or C13:0 3-OH (21.2%) as the main (> 10%) cellular fatty acids. The major polar lipid profile consisted of phosphatidylethanolamine, two unidentified aminolipids, two unidentified phosphoaminolipids and three unidentified lipids. On the basis of distinct phylogenetic and phenotypic evidences, the strain represents a novel species of the genus Spongiibacterium, for which the name Spongiibacterium fuscum sp. nov. is proposed. The type strain of S. fuscum sp. nov. is 04OKA-3-218T (= KCTC 62504T = NBRC 113248T).