Thermithiobacillus is a genus of nonsporeforming, rod-shaped, Gram-negative bacteria.

The name derives from the Latin thermae, for warm baths, and the Classical Greek θείος, theios for sulfur.

[1] A phylogenetic analysis, using 98 protein families confirmed this reassignment.

[2] This chemolithoautotrophic genus is obligately aerobic and moderately thermophilic (43-45 °C).

[1] The type species is Thermithiobacillus tepidarius.