Thermoplasma acidophilum is an archaeon, the type species of its genus.

[1] T. acidophilum was originally isolated from a self-heating coal refuse pile, at pH 2 and 59 °C.

[2] It is highly flagellated and grows optimally at 56 °C (133 °F) and pH 1.8.

T. acidophilum shows various cell shapes depending upon growth conditions and stages.

The full genome of Thermoplasma acidophilum has been sequenced.