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Coal is a readily combustible black or brownish-black rock composed primarily of carbon and formed from plant remains. It is the world's largest single source of fuel for electricity generation, and its fastest growing energy source. It is also the world's largest source of carbon dioxide emissions, one of the key greenhouse gases that are believed to be the primary cause of global warming.

The use of coal dates back to the Bronze Age, but it was the Industrial Revolution that led to its large-scale use, as the steam engine took over from the water wheel. Today world coal consumption is about 5.3 billion tonnes annually, of which about 75% is used to produce electricity. The region including the China and India uses about 1.7 billion tonnes annually, forecast to exceed 2.7 billion tonnes by 2025. The United States consumes about 1.0 billion tons annually. Almost one-third of all coal used was supplied by China in 2005.

Coal mining causes a number of harmful effects, including the pollution of water sources by sulfuric acid caused by a chemical reaction between water and iron sulfide in the coal. In common with other fossil fuels, the burning coal produces carbon dioxide and nitrogen oxides. It also produces sulfur dioxide, the cause of acid rain. Coal contains traces of uranium, thorium, and other naturally-occurring radioactive isotopes which, due to the vast quantities of coal used, cause more radioactive contamination than nuclear power plants. To eliminate CO₂ emissions from coal plants, carbon capture and storage technology has been proposed but has yet to be commercially used.