Swimming is the self-propulsion of a person through water, or other liquid, usually for recreation, sport, exercise, or survival. Locomotion is achieved through coordinated movement of the limbs and the body to achieve hydrodynamic thrust that results in directional motion. Humans can hold their breath underwater and undertake rudimentary locomotive swimming within weeks of birth, as a survival response.

Swimming is consistently among the top public recreational activities, and in some countries, swimming lessons are a compulsory part of the educational curriculum. As a formalized sport, swimming is featured in a range of local, national, and international competitions, including every modern Summer Olympics.

Swimming involves repeated motions known as strokes in order to propel the body forward. While the front crawl, also known as freestyle, is widely regarded as the fastest out of four primary strokes, other strokes are practiced for special purposes, such as for training.

There are various risks present during swimming, mainly due to it taking place in water. Swimmers are at risk of incapacitation due to panic and exhaustion, which may cause death due to drowning. Other dangers include getting an infection or contact with hostile aquatic fauna. To minimize these risks, most facilities employ a lifeguard to look for signs of distress.

Swimmers often wear specialized swimwear, although depending on the culture of the area, some swimmers may also swim nude or wear their day attire. In addition to this, a variety of equipment can be used to enhance the swimming experience or performance, including but not limited to the use of swimming goggles, floatation devices, swim fins, and snorkels.