After sunlight, wind has the most practical potential to supply the world’s all-purpose energy demand. Not only are wind resources abundant in almost every country, but the cost of onshore wind energy has also declined so much that, in 2024, onshore wind, along with utility PV, was the least expensive form of new electricity in many countries. Its low cost has resulted in massive wind installations to replace fossil-fuel power plants and to supply new energy demand. This chapter discusses the history of windmills and wind turbines, followed by a discussion of the different types of wind turbines and wind-turbine components. The chapter also discusses how wind turbines work and how generators convert the mechanical energy from a rotating blade into electricity. Finally, the chapter discusses the wind-farm footprint and spacing areas needed to power the world, wind resources available worldwide, and the impacts of wind turbines on global wind speeds, global temperatures, hurricanes, birds, and bats.