Methanosaeta concilii is a archaeum in the disputed genus Methanosaeta. It is obligately anaerobic, gram-negative and non-motile. It is rod-shaped (length 2.5 to 6.0 μm) with flat ends. The cells are enclosed within a cross-striated sheath. The type strain is GP6 (= DSM 3671 = OGC 69 = NRC 2989 = ATCC 35969). Its genome has been sequenced.