In taxonomy, Picrophilus is an archaean genus of the family Picrophilaceae.

[2] Picrophilus is an extremely acidophilic genus within Euryarchaeota.

These microbes are the most acidophilic organisms currently known,[3] with the ability to grow at a pH of less than 0.5.

They are obligate acidophiles and are unable to maintain their membrane integrity at pH values above 4.

While phylogenetically related to other organisms within Thermoplasmata, unlike Thermoplasma and Ferroplasma, Picrophilus contains an S-layer cell wall.