Phylogenetic relationships of a thermophilic, halophilic, aerobic spore-forming strain 4-1(T), isolated from the water of a shallow sea hot spring at Vulcano Island (Italy), revealed its relatedness to members of the genus Bacillus. Chemotaxonomic and phenotypic properties of strain 4-1(T) are sufficiently different from related moderately thermophilic species, e.g., B. smithii, B. fumarioli, B. oleronius, B. sporothermodurans and B. infernus to describe strain 4-1(T) as a new Bacillus species, for which the name Bacillus aeolius sp. nov. is proposed. Strain 4-1(T) is characterised by the potential biotechnological important properties such as exopolysaccharide production, surfactant activity, and utilisation of hydrocarbons.