Desulforudis audaxviator is a species of bacterium that lives in groundwater at a depth of 2 miles below the surface. The bacteria which was the only found in samples of water obtained 1.74 miles (2.8 km) underground in the Mponeng gold mine near Johannesburg, South Africa.

D. audaxviator is one of the only known organisms that do not depend on sunlight for nourishment, and the only one that is alone in its ecosystem. It survives on chemical food sources derived from the radioactive decay of minerals in surrounding rocks and has genes for extracting carbon and nitrogen fixation. Its genes may have been acquired from a species of archaea through horizontal gene transfer.

D. audaxviator is a Gram-positive sulfate-reducing bacterium, hydrogen for the reduction is derived from the radiolysis of water originating from the decay chain of uranium and thorium. This radiation allows for the production of sulphur compounds which can be used by the bacteria as a high-energy food source. The genome harbors an unusual transposon and possesses numerous insertion sites. Due to its complete intolerance to oxygen, prolonged isolation is suspected.

D. audaxviator lives in the complete absence of organic compounds, light, and oxygen, in temperatures exceeding 140 °F (60 °C). The physiology that enables it to live in these extreme conditions is a tribute to its unusually large genome which consists of 2157 genes rather than the 1500 of bacteria found in very stable environments. It also can form a bacterial endospore to safeguard its DNA from heat, extreme pH, and the lack of water if conditions become unfavorable for normal life.

A 2021 study reported further findings of D. audaxviator in West Siberia, Russia, and Death Valley, California.