Renewable energies refer to a set of means of producing energy from sources or resources theoretically unlimited, available without time limit or replenished more rapidly than they are consumed.

Renewable energies are generally discussed in contrast to fossil fuels, whose stocks are limited and non-renewable on a human time scale: coal, oil, natural gas... Conversely, renewable energies are produced from sources such as sunlight or wind, which are theoretically unlimited on a human scale.

Renewable energies are also sometimes referred to as "green energies" or "clean energies," by linguistic abuse. Indeed, while renewable energies often have ecological advantages, they are not necessarily "green" or "clean" in the sense that they also have significant environmental consequences.