A nude spanking is one in which at least one person, the spankee, is fully nude (naked). This means all clothing, including underwear, shoes, socks, and stockings, must be off. (In BDSM, items such as a collar can be worn and the person is still considered "fully nude".)
This state of full nudity for a spanking goes far beyond that of a mere bare bottom spanking, in which the only requirement is that the buttocks are bared, which can be achieved by pulling down the pants and underwear without a need to take anything off.
In some countries like Singapore and Malaysia, where judicial corporal punishment (in the form of caning) is practiced, prisoners are required to be completely naked (except for special padding that covers vital parts of the body, like the lower back and genitals) when they receive the punishment.
Full nudity in a punishment scenario is generally thought to be more embarassing and humiliating than partial nudity. Still, full nudity is not, as one might be tempted to think, generally considered more erotic than partial nudity. In fact, most spanking artists and spanking art fans prefer a state of only partial undress.
Full nudity can however be particularly suitable to show the beauty of the spankee's body. The contrast of a fully clothed spanker and a fully nude spankee can create a strong visual and emotional impact.
In real life, children are rarely spanked fully naked, except in situations where they are naked anyway (such as bathtime or in societies such as ancient Sparta or in indigenous peoples). Today, in real life, nude spanking is mostly found in adult erotic spanking and sensual spanking. Here, the spanker, too, is sometimes partially or even fully nude. This maximizes skin-to-skin contact e.g. during an OTK spanking, and eases sexual activity during or after the spanking.
 Temperature considerations
For a lengthy spanking session, full nudity can be a problem if the room is not warm enough. The spankee's bottom will surely be warm, but the rest of their body, especially the exposed parts of the torso, legs and feet, can become cold with time. This is the reason why BDSM dungeons are often heated warmer than usual rooms.
 Full nudity in other forms of punishment
Full nudity is also found in other forms of punishment. It can be a punishment in itself, especially in the form of forced nudity in front of other people. It is also commonly found in prectically all forms of BDSM play, including flagellation (of the back and/or other body parts), medical play, wax play and watersports.
 Fetish videos
Videos of erotic corporal punishment and BDSM nearly always include scenes of nude spankees. Many start with partial nudity, especially when fetishistic clothing such as schoolgirl or cheerleader uniforms are featured. Later, the spankee is usually forced to completely undress, often under protest, for the final and most severe punishment segment(s).
Here, nudity is used to accentuate the power dynamic between the characters as well as the helplessness and humiliation of the victim. Two classic examples can be seen in the tense interrogation scenes of political prisoners in Stalin II and Stalin III from Lupus Pictures.
Occasionally, videos designed to emphasize a romantic lesbian relationship will show two nude women in a strict dominant-submissive scenario or a more playful scene of female friends who undress and take turns punishing each other.
Wilhelm Busch, 1878.
Georges Topfer, 1913(?).
Chéri Hérouard, 1932.
G. Whips, c. 1930s.
OTTO, unknown year.
 Almost nude, underwear down
 Almost nude, wearing shoes
In adult spanking art (rarely in child spanking art) it is common to see a (usually female) bottom/spankee almost fully nude, but wearing shoes (and sometimes stockings), instead of bare feet. This comes from the notion that this emphasizes the person's nudity, and also caters for shoe fetishism. Considered particulatly sexy and kinky, the nude-with-high heeled-shoes look became a trademark of the adult erotic genre of the 20th century, found not only in BDSM but also often in mainstream erotica.
Gauis Marius, c. 2007.