Sportswear or activewear is clothing, including footwear, worn for sport 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, T-shirts and polo shirts. Specialized garments include swimsuits (for swimming), wet suits (for diving or surfing), ski suits (for skiing) and leotards (for gymnastics). Sports footwear include trainers, football boots, riding boots, and ice skates. Sportswear also includes bikini and some crop tops and undergarments, such as the jockstrap and sports bra. Sportswear is also at times 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.

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. Yoga clothing should use fabrics with exceptional stretch ability for easy movement which will likely require the fabric to be of a knitted construction. 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.

Functional considerations

On the other hand, sportswear should be loose enough so as not to restrict movement. Some sports have specific style requirements, for example the keikogi used in karate. Various physically dangerous sports require protective gear, e.g. for fencing, American football, or ice hockey.Sportswear is typically designed to be lightweight so as not to encumber the wearer. The best athletic wear for some forms of exercise, for example cycling, should not create drag or be too bulky.

Standardized sportswear may also function as a uniform. In team sports the opposing sides are usually identified by the colors of their clothing, while individual team members can be recognized by a back number on a shirt.

In some sports, specific items of clothing are worn to differentiate roles within a team. For example, in volleyball, the libero (a specialist in defensive play) wears a different colour to that of their teammates. In sports such as soccer and GAA codes, a contrasting colour or pattern is worn by the goalkeeper. In other sports, clothing may indicate the current status or past achievements of a participant. In cycling disciplines, the rainbow jersey indicates the current world champion, and in major road cycling races, jerseys of particular colours are worn by the race leader and leaders of auxiliary classifications.

Spandex is the preferred material for form-fitting sportswear, such as used in wrestling, track & field, dance, gymnastics, speed skating, and swimming.

Sportswear is commonly used as a means for the promotion of sponsors of a sportsperson or team. In some sports, there are regulations limiting the size or design of sponsorship brand names and logos on items of clothing.

Thermal properties

Sportswear design must consider the thermal insulation needs of the wearer. In hot situations, sportswear should allow the wearer to stay cool; while in cold situations, sportswear should help the wearer to stay warm.

Sportswear should also be able to transfer sweat away from the skin, using, for example, moisture transferring fabric. Spandex is a popular material used as base layers to soak up sweat. For example, in activities such as skiing and mountain climbing this is achieved by using layering: moisture transferring (wicking) materials are worn next to the skin, followed by an insulating layer, and then wind and water resistant shell garments.

Moisture-wicking fabrics

Moisture-wicking fabrics are a class of hi-tech fabrics that provide moisture control for an athlete's skin. They move perspiration away from the body to the fabric's outer surface where it can evaporate. These fabrics typically are soft, lightweight, and stretchy—in other words, they are perfectly suited for making activewear. Moisture-wicking means that the fabric is absorbent and this can leave a barrier of wet fabric on your skin. Drywicking is the newest variation of moisture wicking. It is a smart two tier fabric that breaks the surface tension of sweat and propels it through the hydrophobic layer into a natural wicking outer layer like cotton where it is assisted by evaporative cooling leaving your skin absolutely dry. Besides the fact that your body can perform better, it will chemically free prevent odors because a bacteria microclimate cannot grow on dry skin. This broad category of fabrics is used to make garments like T-shirts, sports bras, running and cycling jerseys, socks, tracksuits, and polo-style shirts for any physical activity where the goal is to keep your skin as cool and dry as possible. Moisture-wicking fabrics are used to make apparel for outdoor activities such as hiking, fishing, mountain biking, snow skiing, and mountain climbing. Due to the popularity of garments made from these fabrics, more variations are being introduced to the market.