Piercing is banned on 10 specific intimate body areas
Wales has banned under-18s from having intimate piercings to protect their "health and well-being".
The law comes into force on Thursday and makes it illegal for piercing practitioners to organise or carry out the piercings on anybody under the age of 18.
Piercing is banned on 10 specific intimate body areas - including genital areas, buttocks, nipples and tongues.
Wales is the first country in the UK to introduce the nationwide ban.
In Ireland, there is no legal minimum age to get a piercing or regulation of such businesses.
The chief medical officer for Wales, Dr Frank Atherton, said: "It's concerning that a third of young people with intimate piercings have reported complications following a procedure.
"The child protection issues that could also arise from this scenario highlight even further the importance of implementing such a law.
"I hope this piece of legislation will help to reduce these issues, and that practitioners understand the importance of obtaining proof of age beforehand."
The Welsh government said a study in England found about one-third of all people aged 16 to 24 who had body piercings experienced complications.
Tongue piercings caused the most problems, followed by genital and nipple piercings.
A spokeswoman said: "As young people continue to grow during their teenage years, an intimate piercing performed at a young age could result in further complications arising as their bodies develop.
"Young people may also be less likely to have the experience or knowledge of how to clean or maintain an intimate piercing, leading to an increased risk of infection."
Many dentists and patients welcomed the ban, according to Wales' chief dental officer Dr Colette Bridgman.
She said: "Tongue piercing can lead to lasting damage to teeth and gums, and can cause serious swelling in the mouth that can affect breathing.
"Many dentists in Wales have seen patients who have permanent harm following piercing and dental teams in Wales really welcome this new law."
Piercing artists have been told by the Welsh government to have a "rigid system" in place to ensure they confirm proof of age and gain consent for each procedure.