A washing machine (laundry machine, clothes washer, or washer) is a machine designed to launder clothing. The term is mostly applied to machines that use water. Other ways of doing laundry include dry cleaning (which uses alternative cleaning fluids and is performed by specialist businesses) and ultrasonic cleaning.

Modern-day home appliances use electric power to automatically clean clothes. The user adds laundry detergent, which is sold in liquid, powder, or dehydrated sheet form, to the wash water. The machines are also found in commercial laundromats where customers pay-per-use.

Before the invention of washing machines and indoor plumbing, clothes had to be laboriously washed by hand in a multi-step process that often occupied an entire day of work, plus drying and ironing. The first English patent under the category of washing machines was issued in 1691. Electric washing machines were advertised and discussed in newspapers as early as 1904, and the first automatic washing machine was introduced in 1937. The spread of the washing machine has been seen to be a force behind the improvement of women's position in society, and has been compared to the contraceptive pill, abortion rights, and the refrigerator. Irish feminist Mary Frances McDonald has described washing machines as the single most life-changing invention for women, and Swedish statistician Hans Rosling suggested that its positive impact makes it "the greatest invention of the Industrial Revolution".