A taxonomic study was carried out on strain R8-12(T), which was isolated from deep-sea water of the Indian Ocean during the screening of oil-degrading bacteria. The isolate was Gram-stain-negative, oxidase and catalase-positive. Growth was observed at salinities from 0.5 to 15 % (optimum 3 %), at pH from 6-10 (optimum 7-8) and at temperatures from 10 to 42 °C (optimum 28 °C). On the basis of 16S rRNA gene sequence similarity, strain R8-12(T) was shown to belong to the genus Alcanivorax and to be related to Alcanivorax venustensis DSM 13974(T) (97.2 %), A. dieselolei B-5(T) (95.0 %), A. balearicus MACL04(T) (94.6 %), A. hongdengensis A-11-3(T) (94.3 %), A. jadensis T9(T) (93.8 %), A. borkumensis SK2(T) (93.7 %) and A. pacificus W11-5(T) (93.7 %). The gyrB sequence similarities between R8-12(T) and other species of the genus Alcanivorax ranged from 77.9 % to 86.9 %. The major fatty acids were C16 : 0 (31.8 %), C18 : 1ω7c (20.3 %), C19 : 0ω8c cyclo (15.8 %) and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) (8.9 %). The polar lipids were phosphatidylglycerol (PG), phosphatidylethanolamine (PE), two aminolipids (AL1-AL2) and two phospholipids (PL1-PL2). Three alkane hydroxylase (alkB) genes were identified in the genome. The G+C content of the chromosomal DNA was 66.1 mol%. DNA-DNA hybridization showed that strain R8-12(T) and A. venustensis DSM 13974(T) had a DNA-DNA relatedness of 63±3 %. According to its phenotypic features and fatty acid composition as well as the 16S rRNA and gyrB gene sequences, the novel strain represents a member of the genus Alcanivorax, but could be easily distinguished from all other known species of the genus Alcanivorax described to date. The name Alcanivorax marinus sp. nov. is proposed, with the type strain R8-12(T) ( = MCCC 1A00382(T) = LMG 24621(T) = CCTCC AB 208234(T)).