A rash guard, or rashguard, is a lightweight athletic shirt made from a material like nylon or polyester, engineered to have excellent wicking ability. Rash guards protect the skin from a variety of sporting related hazards, from chafing to sunburn. In addition to being practical, the rash guard has also become a style statement in some parts of the world, especially around surfing communities, where a rash guard may be worn as a casual shirt in addition to a piece of sporting equipment.

One of the major advantages to a rash guard is that the lightweight design allows it to be worn even in very warm weather conditions. Many people like to use rash guards with built-in SPF protection in the tropics to prevent sunburn and keep their skin cool while they surf, snorkle, or swim. Rash guards can also be worn for land sports like tennis, and they may also be worn under other garments.

Classically, a rash guard is worn under a wetsuit to prevent chafing. Prolonged periods of time in a wet suit can cause skin problems, especially in salt water around areas where the suit is bent, like the knees and elbows, with the wrinkled parts of the suit chafing and irritating the skin. By wearing a rash guard, these chafing injuries can be prevented. A rash guard also offers extra insulation for people using a wetsuit in very cold water.

In warm climes, surfers sometimes wear a rash guard alone without a wetsuit, using it for protection from the elements without the bulk and discomfort of a wetsuit. You can also see rash guards used in some martial arts, protecting people from chafing and reducing the amount of time that sweat stays near the skin by wicking it away.

Rash guards come in a variety of sizes and styles, and they do not need to be closely and perfectly fitted to be fully functional. You can find sleeveless rash guards along with rash guards with sleeves of varying lengths at many sporting supply stores, especially those which cater to surfers, and they come in child and adult sizes. For children, a rash guard can be really useful, as it protects delicate skin from sunburn and it is comfortable to wear. If sunburn is a concern, check to be sure that a rash guard comes with an SPF rating, indicating that it has been tested and approved for UV-protection.