Green energy is a term describing what is thought to be environmentally friendly sources of power and energy. Typically, this refers to renewable and non-polluting energy sources.

Green energy includes natural energetic processes which can be harnessed with little pollution. Anaerobic digestion, geothermal power, wind power, small-scale hydropower, solar power, biomass power, tidal power and wave power fall under such a category.

Some versions may also include power derived from the incineration of waste.

More controversial is nuclear energy's claim to be green. It is possibly sustainable, arguably renewable and produces virtually no atmospheric pollution during the energy production stage. However nuclear waste is a pollutant, as well as the carbon dioxide and other greenhouse gases generated by the large amount of energy required by transport, mining and pre- and post-production. Hence, nuclear power is rarely included in official green energy schemes.

Likewise, medium or large-scale hydroelectric power or sources of air pollution such as burning biomatter or petroleum, are often excluded from the label 'green energy'.