<jats:p>Four strains of cold-adapted, strictly aerobic and facultative oligotrophic bacteria were isolated from polar seas and investigated using a polyphasic taxonomic approach. Two strains (LMG 21857<jats:sup>T</jats:sup> and LMG 21854) derive from Arctic sea water whereas the other two strains (LMG 21855 and LMG 21858) were isolated from Antarctic sea water. Phylogenetic analysis based on 16S rRNA gene sequences indicated that these strains belong to the <jats:italic>γ</jats:italic>-subclass of the <jats:italic>Proteobacteria</jats:italic> and are related to the genus <jats:italic>Glaciecola</jats:italic>, with 98·0–99·7 % sequence similarity to <jats:italic>Glaciecola mesophila</jats:italic> and 94·2–95·3 % sequence similarity to <jats:italic>Glaciecola punicea</jats:italic>, their nearest phylogenetic neighbours. Two strains (LMG 21855 and LMG 21858) were identified as <jats:italic>G. mesophila</jats:italic>, whereas DNA–DNA hybridization results and differences in phenotypic characteristics showed that the other two strains (LMG 21857<jats:sup>T</jats:sup> and LMG 21854) constitute a novel species within the genus <jats:italic>Glaciecola</jats:italic>, with a DNA G+C content of 44·0 mol%. The isolates are Gram-negative, chemoheterotrophic, motile, rod-shaped cells that are psychrotolerant and moderately halophilic. Buds can be produced on mother cells and on prosthecae. Branch formation of prosthecae occurs. Whole-cell fatty acid profiles of the isolates are very similar and include C<jats:sub>16 : 0</jats:sub> and C<jats:sub>16 : 1</jats:sub> <jats:italic>ω</jats:italic>7<jats:italic>c</jats:italic> as the major fatty acid components. On the basis of genotypic and phenotypic properties, a novel species of the genus <jats:italic>Glaciecola</jats:italic> is described, for which the name <jats:italic>Glaciecola polaris</jats:italic> sp. nov. is proposed, with isolate LMG 21857<jats:sup>T</jats:sup> (=CIP 108324<jats:sup>T</jats:sup>=ARK 150<jats:sup>T</jats:sup>) as the type strain. An emended description of the genus <jats:italic>Glaciecola</jats:italic> is presented.</jats:p>