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.

In wealthy and rising economies, sportswear is a major consumption category in the personal health, luxury goods and leisure space, associated with aggressive media presence and marketing strategies of global scope, often centered around endorsements from celebrity athletes. At the very highest levels of performance, the durability requirement of a costly and technically advanced item of sportswear can be as short as a single competitive event. At lower levels of competition and participation, there are many possible trade-offs between form, function, aesthetics (fashion), performance style, durability and cost. This has led to an almost bewildering array of product offerings, especially where the collision between all these variables is most intense, in particular footwear (most especially runners and court shoes), with seasonal issues, tweaks, and respins from all the major brands, elevated to the level of iconic symbols in some cultural subgroups.