Jockstraps, also known as athletic supporters, are men's undergarments for use in sports and other activities, although they are also worn in other circumstances, for example during the recovery from a vasectomy. They are also worn by some people as general, everyday underwear. The typical jockstrap consists of an elastic waistband with a support pouch for the genitals and two straps extending from the bottom of the pouch across the buttocks to the waistband.

Some jockstraps have pockets for a protective cup (UK: box), usually with a padded rim and made of hard plastic, sometimes with ventilation holes. Cups are worn by baseball and cricket players and others participating in full-contact sports. There are both soft cups and hard cups.

Cups are currently available in two basic shapes. The classic shape is approximately rectangular when viewed from the front. The much newer shape is more like a long skinny triangle. This shape is also known as a banana cup after the brand that specializes in the shape. The banana shaped cups are regarded to be far more comfortable to wear.

Cup protectors that don't use a pouch are also available. The waist band and straps attach directly to the cup often in a one size fits all fashion. These are designed to be worn over briefs, especially if the cup has holes in it. Otherwise the scrotum can be painfully pinched in the cup hole. Some also dislike jockstrap underwear because it sometimes lets the pubic hair show, due to it's long slender shape.

Other types of jocks have narrow waistbands, (swimmer jocks or runner jocks), wide waistbands or have a seat instead of straps (jock briefs, or support briefs).

Jockstraps were first developed in the late 1800's to be worn by bicycle delivery boys by the Bike Company. Bike is still the market leader. Other well-known brands include The Duke, Flarico, Adams, Champion, Ace, Bauer & Black, Safe-T-Guard, Franklin, Pro Sport, Stromgen, McDavid, Futuro, Core, Sportjock, etc.