Fossil hydrocarbons are hydrocarbons (organic compounds consisting mostly of hydrogen and carbon atoms) that have been formed by the action of anaerobic microorganisms on the remains of ancient life, such as plant material, that has been subjected to high heat and pressure over millions of years. These organic compounds are the primary source for petroleum products, such as gasoline and diesel, and are a major contributor to the current energy mix and climate change due to their climate-forcing emissions.

See also: fossil fuel, fossil carbon, nuclear power, nuclear fuel, energy surplus