A bouffant cap is a hat whose function is to keep stray hair in and water or other contaminants out. It resembles a bag with a gathered elastic opening that covers the hair and fits snugly around the hairline. A bouffant cap is traditionally used to protect a complicated hairstyle while sleeping or showering. It is also used by the medical profession and in food preparation, keeping stray hairs under the cap.

Taking its name from the bouffant or beehive hairstyle that was popularized by style icons Marie Antoinette and later Bridgette Bardot, the bouffant cap has been around for a long time. Originally, it was made out of soft fabric, which was tailor made to fit the owner. More modern versions are made out of plastic, netting, or polypropylene, making a disposable bouffant cap a cheap and practical solution for a variety of applications.

Bouffant caps are an important beauty tool used to protect hair. Hair that is very fragile or easily tangled can be protected at night by sleeping in a silk-lined bouffant cap. A special-occasion hairstyle that takes a lot of time to do and lots of hairspray and pins to hold in place can be protected while dressing or doing make-up.

Bouffant caps can also be used to keep messy hair treatments from ruining clothes or furniture. A plastic bouffant cap trap some of the harsh chemicals, odors, and fumes from coloring or perming hair. This prevents toxins from being inhaled. It also prevents accidental drips that could bleach or stain fabrics.

There are three ways that plastic bouffant caps can be used with heat-activated hair masks. After applying the mask, cover hair with the cap. The first method is to cover the head with a warm towel. The second method is to stand under a warm shower. The third method is to use a hair dryer set to a warm setting to gently heat the hair. The bouffant cap lets the heat in while preventing the hair mask from being removed, watered down, or dried up.

Many other professional uses of bouffant caps exist. Bouffant surgical caps are commonly worn by doctors who need to maintain a sterile environment and cannot risk leaving stray hairs. Bouffant hair nets are used in food preparation to avoid hairs from falling into food.