A jockstrap, also a jock (male), jill (female), strap, cup, groin guard, pelvic protector (female), supporter, or athletic supporter, is an undergarment for protecting the testes and penis or vulva during contact sports or other vigorous physical activity. This article deals chiefly with the genital protective sports gear designed for the male body, colloquially known as a "jock".

A jockstrap (males) consists of a waistband (usually elastic) with a support pouch for the genitalia and two elastic straps affixed to the base of the pouch and to the left and right sides of the waistband at the hip. The pouch, in some varieties, may be fitted with a pocket to hold an abdominal guard (impact resistant cup, box) to protect the testicles and the penis from injury.

The jillstrap (a.k.a. a "jill") is the female equivalent of the jockstrap, but is designed to protect the vulva from getting struck.