A slightly beige-white pigmented, Gram-staining-negative, rod-shaped bacterium, strain M1A1(T), was isolated from seawater samples obtained in Fildes Bay, Antarctica (62 degrees 12'S 58 degrees 57' W). Phylogenetic analysis based on nearly full-length 16S rRNA gene sequences showed that the isolate shared 98.4% 16S rRNA gene sequence identity to the type strain of Psychromonas arctica, but less than 97% 16S rRNA gene sequence similarities to all other species of the genus Psychromonas. DNA-DNA hybridization with Psychromonas arctica DSM 14288(T) showed low values (21 %, reciprocal 27 %). The main cellular fatty acid of strain M1A1(T) was summed feature 3 fatty acids (C(16 : omega)7c/C-16 : 1 omega 8c), followed by C-16 : 0. Based on phylogenetic, chemotaxonomic, genomic and phenotypic analyses, we propose a novel species of the genus Psychromonas with the name Psychromonas aquatilis sp. nov. and the strain M1A1(T) (= CIP 111183(T) = CCM 8710(T) = LMG 29766(T)) as type strain.