A Gram-stain-negative, non-motile and rod-shaped bacterium, designated as strain W52T, was isolated from deep seawater of the Mariana Trench and characterized phylogenetically and phenotypically. The strain could grow at 10-47 °C (optimum 32 °C), at pH 5.0-8.0 (optimum 6.0) and with 0-9% NaCl (optimum 3 %, w/v). The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that W52T was related to members of the genus Muricauda and shared the highest identity with Muricauda oceani 501str8T (99.0 %), followed by Muricauda aquimarina JCM 11811T, Muricauda ruestringensis DSM 13258T, Muricauda oceanensis 40DY170T, Muricauda beolgyonensis KCTC 23501T and Muricauda zhangzhouensis 12C25T with 97.0-98.8 % sequence similarity. 16S rRNA gene sequence identities between W52T and other members of the genus Muricauda were below 97.0 %. The major respiratory quinone was MK-6. The polar lipids were phosphatidylethanolamine (PE), one unidentified aminolipid and three unidentified lipids. The strain had iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 1G as the major fatty acids. The G+C content of the genomic DNA was 41.7 %. The combined genotypic and phenotypic data indicated that strain W52T represents a novel species of the genus Muricauda, for which the name Muricauda abyssi sp. nov. is proposed, with the type strain W52T (=MCCC 1K05111T= KCTC 82315T).