A novel endospore-forming bacterium designated strain GSsed3T was isolated from deposits clogging aboveground filters from the geothermal power platform of Groß Schönebeck in northern Germany. The novel isolate was Gram-staining-positive, facultatively anaerobic, catalase-positive and oxidase-positive. Optimum growth occurred at 60 °C, 0.5 % (w/v) NaCl and pH 7-8. Analysis of the 16S rRNA gene sequence similarity indicated that strain GSsed3T belonged to the genus Anoxybacillus, and showed 99.8 % sequence similarity to Anoxybacillus rupiensis R270T, 98.2 % similarity to Anoxybacillus tepidamans GS5-97T, 97.9 % similarity to Anoxybacillus voinovskiensis TH13T, 97.7 % similarity to Anoxybacillus caldiproteolyticus DSM 15730T and 97.6 % similarity to Anoxybacillus amylolyticus MR3CT. DNA-DNA hybridization (DDH) indicated only 16 % relatedness to Anoxybacillus rupiensis DSM 17127T. Furthermore, DDH estimation based on genomes analysis indicated only 19.9 % overall nucleotide similarity to Anoxybacillus amylolyticus DSM 15939T. The major respiratory menaquinone was MK-8. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unknown phosphoglycolipid and one unknown phospholipid. The predominant cellular fatty acids were iso-C15 : 0, iso-C17 : 0, C16 : 0, iso-C16 : 0 and anteiso-C17 : 0. The peptidoglycan type was A1γ meso-Dpm-direct. The genomic DNA G+C content of the strain was 46.9 mol%. The phenotypic, genotypic and chemotaxonomic characterization indicated that strain GSsed3T differs from related species of the genus. Therefore, strain GSsed3T is considered to be a representative of a novel species of the genus Anoxybacillus, for which the name Anoxybacillus geothermalis sp. nov. is proposed. The type strain of Anoxybacillus geothermalis is GSsed3T (=CCOS808T =ATCC BAA2555T).