A nude beach, sometimes called a clothing-optional or free beach, is a beach where users are at liberty to be nude. Nude beaches usually have mixed bathing. Such beaches are usually on public lands, and any member of the public is allowed to use the facilities without membership in any movement or subscription to any personal belief. The use of the beach facilities is normally anonymous. Unlike a naturist resort or facility, there is normally no membership or vetting requirement for the use of a nude beach. The use of nude beach facilities is usually casual, not requiring pre-booking. Nude beaches may be official (legally sanctioned), unofficial (tolerated by residents and law enforcement), or illegal.

The number of nude beaches in some countries is relatively low, and they are generally located some distance away from the city. Access is at times more difficult than at a regular beach and the facilities at these beaches tend to be very basic with a few notable exceptions. In other countries, like Denmark, most beaches are clothing-optional. Nude swimming is one of the most common forms of nudity in public. A nude beach should not be confused with a topless beach (or top-free beach), where upper body clothing is not required for women or men, although a swimming costume covering the genital area is required for both men and women. A nude beach should be considered as a clothes-free beach.

Nude beaches tend to be separate or isolated physically from non-nude bathing areas. In other instances people maintain a comfortable space between beach users. Signage is often used to warn unfamiliar beach users about the specially designated areas on the beach. This accommodates people who are not comfortable with nudity, as well as nude beach users who do not like to be watched by clothed individuals, particularly those engaged in voyeurism.

There are several categories of nude beaches:

Most beaches around the world, including nude beaches, are on public lands. That means that although private resorts and hotels that adjoin a beach may enclose their property behind fences with controlled access, most countries do not allow private ownership of the actual beach area. Thus, while a resort can control access and set clothing standards on its property, these standards would not necessarily apply to the beach itself, which remains subject to local laws or customs, and public access to the beach itself usually remains unrestricted. This applies, for example, to the islands in the Caribbean, Mexico, and Florida. On the Seven Mile Beach in Negril, Jamaica, for example, though the beach is lined with private resorts with fences down to the sand/waterline, the beach itself is open to the public. Though actual clothing standards vary from resort to resort, the beach area is officially designated as "topfree", and public access is unrestricted.

The Hibiscus Coast Local Municipality in South Africa formalize an existing clothing-optional beach within the Mpenjati Nature Reserve.

There are eight officially regulated naturist beaches in Brazil, but they are not "clothing optional". Nudity is required, and single men are not allowed unless they have a membership card from a recognized naturist organization. Otherwise, they are similar to other self-regulated naturist beaches, asserting that nudity is natural, and need not be sexual.

The International Naturist Federation has developed a code of conduct, or etiquette, for use by member organizations. The INF nude beach etiquette requires the avoidance of all forms of sexual harassment and sexual activity, such as masturbation or sexual intercourse. Predatory behavior is not permitted, nor is unauthorized photography. In general, the standards call for the respecting of the privacy of other visitors. Staring is frowned upon by rule and social pressure.