A wind turbine is a device that converts the kinetic energy of wind into electrical energy. As of 2020, hundreds of thousands of large turbines, in installations known as wind farms, were generating over 650 gigawatts of power, with 60 GW added each year. Wind turbines are an increasingly important source of intermittent renewable energy, and are used in many countries to lower energy costs and reduce reliance on fossil fuels. One study claimed that, as of 2009, wind had the "lowest relative greenhouse gas emissions, the least water consumption demands and the most favorable social impacts" compared to photovoltaic, hydro, geothermal, coal and gas energy sources.

Smaller wind turbines are used for applications such as battery charging and remote devices such as traffic warning signs. Larger turbines can contribute to a domestic power supply while selling unused power back to the utility supplier via the electrical grid. Wind turbines are manufactured in a wide range of sizes, with either horizontal or vertical axes, though horizontal is most common.

The very first wind turbine that produced electricity was created by Professor James Blyth at his holiday home in Scotland in 1887. It was 10m high and had a sail cloth. The world’s first wind farm opened in New Hampshire in the US in 1980. By 2014, over 240,000 commercial-sized wind turbines were operating in the world, producing 4% of the world's electricity. The countries in the world with the most wind farms are China, the United States, Germany, Spain, India, the United Kingdom, and Denmark.

Wind turbines is one of the lowest-cost sources of renewable energy along with solar panels. As technology needed for wind turbines continued to improve, the prices decreased as well. In addition, there is currently no competitive market for wind energy (though there may be in the future), because wind is a freely available natural resource, most of which is untapped. The main cost of small wind turbines is the purchase and installation process, which averages between $48,000 and $65,000 per installation. Usually, the total amount of energy harvested amount to more than the cost of the turbines.

Wind turbines provide a clean energy source, use little water, emitting no greenhouse gases and no waste products during operation. Over 1,400 tonnes (1,500 short tons) of carbon dioxide per year can be eliminated by using a one-megawatt turbine instead of one megawatt of energy from a fossil fuel.

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