Strain 435T, a catalase- and oxidase-positive, beige-pigmented, facultatively anaerobic and Gram-stain-negative marine bacterium, was isolated from marine sediment collected in the Arctic (8°21′629′′E 72°8′827′′N). The cells of the type strain are short- to curve-rods and able to grow at 4–25 °C, pH 6.0–9.0 and in the presence of 0.5–6.0 % (w/v) NaCl. It can reduce nitrate to nitrite. The predominant isoprenoid quinone was identified as Q-8 and the polar lipids are comprised of phosphatidylethanolamine and phosphatidylglycerol. The DNA G+C content is 38.7 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 435T belongs to the genus Colwellia. Strain 435T was found to exhibit 92.1–95.6 % 16S rRNA gene sequence similarities with other species of the genus Colwellia. The differential phenotypic properties, together with the phylogenetic and genetic distinctiveness indicated that strain 435T can be considered to represent a novel species, Colwellia arctica sp. nov., of the genus Colwellia. The type strain is 435T (=CICC 10860T = ATCC BAA-2609T).