A nipple shield is a piece of body jewelry worn on the nipple, partially or fully covering the areola. The shield encircles the nipple, and can be stuck on by various means, including suction, friction and the action of glue, but is most often held in place by a nipple piercing. Usually, the primary intent of the nipple shield is to lift, highlight, and ornament the nipple, as well as the whole breast, much as other pieces of jewelry do for other parts of the body.
A shield, particularly the type known as a breast petal, can also be worn to smooth the transition between nipple and breast, so as to disguise the protuberant feature and present a smoother clothed profile. As a breast petal covers the whole nipple and areola, it is, perhaps, better considered a type of pasty, an item of clothing designed to do this.
A nipple shield was infamously shown on television in the United States, and around the world, as part of Janet Jackson's wardrobe malfunction during the Super Bowl XXXVIII halftime show.