A new thermophilic, xylanolytic, strictly anaerobic, rod-shaped bacterium, strain SEBR 7054T, was isolated from an African oil-producing well. Based on the presence of an outer sheath (toga) and 16S rRNA sequence analysis data, this organism was identified as a member of the genus Thermotoga. Strain SEBR 7054T possessed lateral flagella, had a G+C content of 50 mol%, produced traces of ethanol from glucose but no lactate, and grew optimally in the presence of 0 to 0.2% NaCl at 70°C. Its phenotypic and phylogenetic characteristics clearly differed from those reported for the five previously validly described Thermotoga species. Therefore, we propose that strain SEBR 7054T is a member of a new species of the genus Thermotoga, Thermotoga hypogea sp. nov. The type strain of T. hypogea is SEBR 7054 (= DSM 11164).