Abiogenic petroleum origin is an alternative hypothesis to the prevailing theory of biological petroleum origin. Most popular in the Soviet Union between the 1950s and 1980s, the abiogenic hypothesis has little support among contemporary petroleum geologists, who argue that abiogenic petroleum does not exist in significant amounts and that there is no indication that an application of the hypothesis is or has ever been of commercial value. The abiogenic hypothesis argues that petroleum was formed from deep carbon deposits, perhaps dating to the formation of the Earth. The presence of methane on Saturn's moon Titan is cited as evidence supporting the formation of hydrocarbons without biology. Supporters of the abiogenic hypothesis suggest that a great deal more petroleum exists on Earth than commonly thought, and that petroleum may originate from carbon-bearing fluids that migrate upward from the mantle. Although the abiogenic hypothesis was accepted by some geologists in the former Soviet Union, most geologists now consider the biogenic formation of petroleum scientifically supported. studies indicate they are not produced in commercially significant quantities (i.e. a median abiogenic hydrocarbon content in extracted hydrocarbon gases of 0.02%). The abiogenic origin of petroleum has also recently been reviewed in detail by Glasby, who raises a number of objections, including that there is no direct evidence to date of abiogenic petroleum (liquid crude oil and long-chain hydrocarbon compounds). Although the biogenic theory for petroleum was first proposed by Georg Agricola in the 16th century, various abiogenic hypotheses were proposed in the nineteenth century, most notably by Alexander von Humboldt, the Russian chemist Dmitri Mendeleev and the French chemist Marcellin Berthelot. Since that time, the abiogenic hypotheses have lost ground to the view that petroleum is a fossil fuel. Abiogenic hypotheses were revived in the last half of the twentieth century by Russian and Ukrainian scientists, and more interest was generated in the West by the publication in 1999 of The Deep Hot Biosphere by Thomas Gold. Gold cited the discovery of thermophile bacteria in the Earth's crust as new support for the postulate that these bacteria could explain the existence of certain biomarkers in extracted petroleum.

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