Three novel isolates (A-354T , A-328, and A-384) were retrieved from apparently healthy scleractinian Madracis decactisin the remote St Peter & St Paul Archipelago, MidAtlantic Ridge, Brazil. The novel isolates formed a distinct lineage based on the phylogenetic reconstruction using the 16S rRNA and pyrH gene sequences. They fell into the Mediterranei clade and their closest phylogenetic neighbour was V. mediterranei species, sharing upto 98.1 % 16S rRNA gene sequence similarity. Genomic analysis including in silico DDH, MLSA, AAI and genomic signature distinguished A-354T from V. mediterranei LMG 19703 (=AK1) with values of 33.3, 94.2, 92 %, and 11.3, respectively. Phenotypically, the novel isolates can be differentiated from V. mediterranei based on the four following features. They do not grow at 8 % NaCl; use D-gluconic acid but not L-galactonic acid lactone as carbon source; and do not have the fatty acid C18:0. Differentiation from both the other Mediterranei clade species (V. maritimus and V. variabilis) is supported by fifteen features. The novel species show lysine decarboxylase and tryptophan deaminase, but not gelatinase and arginine dihydrolase activity; produce acetoin; use a-D-lactose, N-acetyl-D-galactosamine, myo-Inositol, D-gluconic acid, and b-hydroxy-D,L-butyric acid; and present the fatty acids C14:0 iso, C15:0 anteiso, C16:0 iso, C17:0 anteiso, and C17:1x8c. Wholecell protein profiles, based on MALDI-TOF, showed that the isolates are not clonal and also distinguished them from the closes phylogenetic neighbors. The name Vibrio madracius sp. nov. is proposed to encompass these novel isolates. The G?C content of the type strain A-354T (=LMG 28124T =CBAS 482T ) is 44.5 mol%