The law will mean everyone in France must verify their age to access social media and comes as the UK and EU are developing their own limits in response to concerns for children's mental health.
French President Emmanuel Macron has welcomed the move, which he had pledged to introduce to mark the end of his decade in office.
While sceptics have questioned the law's viability, the government has insisted the online tools to put the age checks in place are effective and safe.
Both the French Senate and National Assembly adopted the ban on Tuesday, despite criticism from some on the left.
It will be implemented in two stages:
- From September, people under 15 will not be able to open accounts and age verification will be required on all new accounts
- In January 2027, this rule will apply to all existing accounts meaning everyone in France will have to prove they are over 15 to use social media
Once the ban is in place, social media platforms would need to use age-verification tools approved by the French privacy regulator, according to Reuters news agency.
But concerns have been raised over privacy, the efficacy of age-verification tools, the risks of young people bypassing them, and how quickly the ban has been designed and brought in, Agence France Presse reports.
French Digital Minister Anne Le Hénanff defended the speed of the law's implementation ahead of the vote "because age-verification tools already exist", the agency added.
France is the second country to introduce a ban, following Australia.
Despite Australia banning under-16s from social media in December, it is widely acknowledged that many continue to use the platforms.
