A spore-forming, halophilic bacterium was isolated from surface sediment located on the beach of Palaeochori Bay near to a shallow water hydrothermal vent area, Milos, Greece. The bacterium, designated SH 714T, consisted of motile, strictly aerobic rods which contained an Orn-D-Glu type murein and a G+C content of 35 mol%. Thin sections showed a cell wall typical for Gram-positive bacteria; the peptidoglycan layer, however, was very thin. The Gram-reaction of the organism was negative. Comparative 16S rRNA gene sequencing demonstrated that the isolate represents a new line of descent within the spore-forming rods branching at the periphery of the rRNA group 1 Bacillus (Bacillus sensu stricto). The nearest phylogenetic neighbours of the unknown bacterium were Bacillus haloalkaliphilus, Marinococcus albus and Halobacillus species. Based on phylogenetic and phenotypic evidence it is proposed that the unknown bacterium be classified as Filobacillus milensis gen. nov., sp. nov. The type strain is SH 714T (= DSM 13259T = ATCC 700960T).