On Thursday, the parliament voted unanimously to make rape with children below 15 a punishable offence, inviting up to 20 years in jail.
The long stand-law comes after the country was rocked by series of sex abuse scandals for years and allegations of incestuous abuse plagued the French elite.
“This is an historic law for our children and our society,” justice minister Éric Dupond-Moretti said in the National Assembly on Thursday.
The activists and supporters believe that the new law will make it easy to prosecute predators and serial offenders.
“No adult aggressor will be able to claim the consent of a minor younger than 15 years old,” Mr Dupond-Moretti said.
Previous laws allowed consent of a person to be accepted by the court irrespective of the age, that included adults having sex with children or making incest relations.
Although the sex between adults and under-5s was prohibited but allowed consent of under 15s, making it extremely difficult for the prosecutors to prove allegations of child rape.
However, a so-called "Romeo and Juliet" clause was added to the law which still makes it possible for teenagers to consent to sex with a minor, who is above five years of age. The clause will not apply to cases of sexual assault.
This clause was added after concerns were raised by lawmakers that setting the age of consent at 15 will automatically criminalise a sexual relationship between young partners of the same age.
The legislation has also toughened laws on incestuous sex as thousands of women who were the victim of the sexual crimes testified they were abused by their relatives.
The country that has long cherished its image as the land of seduction and romance was marred by exposé of sex scandals after the #MeToo movement swept across France, after the step daughter of prominent academic Olivier Duhamel accused him of abusing her twin brother as a child.
It led to more people coming forward to testify with the hashtag #MeTooIncest.
The country previously toughened sex crimes laws in 2018 when it outlawed sexual harassment on the streets, with spot-on fines for eve-teasers and catcallers.