A Gram-stain-negative, aerobic, rod-shaped, non-spore-forming bacterium (SV325(T)) was isolated from the sediment of a hypersaline lake located 4600 m above sea level (Laguna Vilama, Argentina). Strain SV325(T) formed cream to pink colonies, was motile and moderately halophilic, and tolerated NaCl concentrations of 1-25 % (w/v) with an optimum of 5-10 % (w/v). Growth occurred at 5-40 °C (optimum around 30 °C) and at pH 5.0-10.0 (optimum 7.0-8.0). The bacterium did not produce exopolysaccharides and stained positively for intracellular polyphosphate granules but not for poly-β-hydroxyalkanoates. It produced catalase and oxidase, reduced nitrate to nitrite, hydrolysed gelatin, did not produce acids from sugars and utilized a limited range of substrates as carbon and energy sources: acetate, caproate, fumarate, dl-β-hydroxybutyrate, malate, maleate, malonate and succinate. The predominant ubiquinones were Q-9 (92.5 %) and Q-8 (7.5 %), the major fatty acids were C(19 : 0) cyclo ω8c, C(16 : 0), C(17 : 0) cyclo and C(16 : 1)ω7c/iso-C(15:0) 2-OH, and the DNA G+C content was 55.0 mol%. Phylogenetic analyses based on the 16S rRNA gene indicated that strain SV325(T) belongs to the genus Halomonas in the class Gammaproteobacteria. Physiological and biochemical tests allowed phenotypic differentiation of strain SV325(T) from closely related species with validly published names. We therefore propose a novel species, Halomonas vilamensis sp. nov., with type strain SV325(T) ( = DSM 21020(T) = LMG 24332(T)).