Sportswear or activewear is athletic clothing, including footwear, worn for sports activity or physical exercise. Sport-specific clothing is worn for most sports and physical exercise, for practical, comfort or safety reasons.

Typical sport-specific garments include tracksuits, shorts, football or basketball jerseys, t-shirts and polo shirts. Specialized garments include swimsuits (for swimming), wet suits (for diving or surfing), ski suits (for skiing) and leotards and tights (for gymnastics or aerobics). Sports footwear includes football boots (also referred to as cletes), trainers, riding boots, tennis shoes (or running shoes), or ice skates. Sportswear also includes sports bras for running, crop tops, or a bikini top. Sportswear is often worn as casual fashion clothing.

For most sports the athletes wear a combination of different items of clothing, e.g. sport shoes, pants and shirts. In some sports, protective gear may need to be worn, such as helmets or American football body armour. Especially in team sports which involved blocking, intercepting, or pursuing small, hard projectiles such as cricket, baseball, and hockey (where balls or pucks are struck to speeds in excess of 100 miles per hour (45 m/s)) jockstraps (or jillstraps) are standard equipment at higher levels of play. Other undergarments, such as the sports bra, furnish a mixture of protection, support and comfort. Some protective or supportive orthotics resemble and function as undergarments (especially flexible harnesses and braces); though intended to be worn for sports, these are not generally conceived of as sportswear per se.

Sports fabrics are technical materials which help to keep the wearer comfortable during exercise. The type of fabric required will depend upon the intensity of the exercise and the activity. Gym or Yoga clothing uses fabrics with exceptional stretch ability for easy movement which will likely require the fabric to be cotton, nylon or lycra. Apparel for long-distance running will keep the wearer in good comfort if it has excellent moisture wicking properties to enable sweat to transfer from the inside to the outside for the garment. Performance clothing for outdoor sports in the winter or snow sports should use breathable fabrics with very good insulating properties.

The weight, fabrication and stretchiness of the fabric are uniquely designed to suit each sport. It is typically designed not to encumber the activity of the wearer and to facilitate exercise movement without restriction.

The best athletic wear for some forms of exercise, for example cycling, is typically lightweight, stretchy and form-fitting rather than bulky, so it does not create interference with the activity.

On the other hand, sportswear should be loose enough to restrict movement. Some sports have specific uniform requirements, for example the keikogi used in karate. Various physically dangerous sports require protective gear, e.g. for fencing, American football, or ice hockey.

Standardized sportswear may also function as a uniform. In team sports, such as baseball, football or basketball, the opposing teams are usually identified by the wearing the same color of clothing. Individual team members can be recognized by a back number on a shirt.