It would be the first law of its kind in France, where there is now no law that states a child below a certain age is considered incapable of consenting to sex.
The reform on Tuesday comes following two recent cases where men avoided rape charges despite having sex with 11-year-old girls.
The change is part of a wider law "against sexist and sexual violence" that will be presented to the council of ministers on March 21.
While the punishment for rape when a victim is younger than 15 carries a heftier penalty under French law (20 years), prosecutors must prove that the sex was forced.
Under existing laws, if violence and force can't be proven, offenders may only be charged with sexual abuse of a minor and not with rape.
Ms Schiappa said the government "decided to set the age at 15" after consultations with doctors and legal experts.More news: REI stops ordering products made by company that also makes guns
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In another case, a man, who is now 28, has faced charges of sexual assault rather than rape, which has enraged the family and public. This decision comes after two high-profile cases of rape involving 11 year-old girls which has sparked outrage throughout the land.
In November, a 30-year-old man was acquitted of the rape of an 11-year-old girl after the court determined she had not been subjected to "constraint, threat, violence or surprise".
Schiappa told reporters she was "very glad" that the government chose to formalize the age of consent, a move that she hopes will combat the prevalence of rape culture in France. In addressing rape culture, she told CNN, "We want to fix an age in the law below which it's always forbidden to have sex with children, with young girls".
If the child is under 15 years of age, the new law will put the onus on the adult to prove the minor gave consent, instead of expecting the victim to prove they were threatened, coerced, or surprised.
But last month, the same court reversed its decision, saying the accused should indeed face rape charges - though it asked for the trial to be moved to a higher court. The limit is also supported by President Emmanuel Macron.