Two moderately psychrophilic actinobacterial strains, designated AU-G6T and AU-A3.2, isolated from the surface of an Antarctic macroalga, Adenocystis utricularis (Bory) Skottsberg, was taxonomically characterized based on a polyphasic investigation. The two strains had nearly identical 16S rRNA gene sequences and formed a distinct phyletic line within the genus Amycolatopsis of the family Pseudonocardiaceae. They were phylogenetically close to Amycolatopsis nigrescens JCM 14717T, Amycolatopsis minnesotensis JCM 14545T and Amycolatopsis magusensis DSM 45510T, with 16S rRNA gene sequence similarities of 97.77, 97.20 and 97.19 %, respectively. Phylogenomic analysis based on the whole genome data supported that strain AU-G6T was distantly related to the Amycolatopsis species. The isolates shared a range of phenotypic markers typical of members of the genus Amycolatopsis, but also had a range of cultural, physiological and biochemical characteristics that separated them from related Amycolatopsis species. The isolates showed growth only in media supplemented with salt, indicating their marine origin. The cell wall of the isolates contained meso-diaminopimelic acid, and arabinose and galactose were detected as diagnostic sugars (type IV). The main menaquinone was MK-9(H4). The main polar lipids were phosphatidylethanolamine, hydroxy-phosphotidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol (type II). The fatty acid type was 3c. The combined genotypic and phenotypic data indicated that the two isolates represent a novel species of the genus Amycolatopsis. The name proposed for this species is Amycolatopsis antarctica sp. nov., with type strain AU-G6T (=CGMCC 4.7351T=NBRC 112404T).