An obligately aerobic, Gram-negative, non-spore-forming, non-motile, spherical bacterium, designated strain 04OKA010-24T, was isolated from seawater surrounding the hard coral Galaxea fascicularis L., collected at Majanohama, Akajima, Japan, and was subjected to a polyphasic taxonomic study. Phylogenetic analyses based on the 16S rRNA gene sequence indicated that the new strain represented a member of the phylum ‘Verrucomicrobia’ and shared 84–95 % sequence similarity with cultivated strains of ‘Verrucomicrobia’ subdivision 4. Amino acid analysis of the cell-wall hydrolysate indicated the absence of muramic acid and diaminopimelic acid, which suggested that the strain did not contain peptidoglycan in the cell wall. The G+C content of the DNA was 53.9 mol%. MK-7 was the major menaquinone and C14 : 0, C18 : 1 ω9c and C18 : 0 were the major fatty acids. On the basis of these data, it was concluded that strain 04OKA010-24T represents a novel species in a new genus in subdivision 4 of the phylum ‘Verrucomicrobia’, for which the name Coraliomargarita akajimensis gen. nov., sp. nov. is proposed. The type strain of Coraliomargarita akajimensis is 04OKA010-24T (=MBIC06463T=IAM 15411T=KCTC 12865T).