French citizenship by descent: who is French, how to prove it

French nationality by descent is not something you apply for. If one of your parents was French on the day you were born, you are French from birth, wherever you were born and whether or not your parents were married, provided the link with that parent was established while you were a minor.

What you may need is proof, and that is where most files get stuck.

How it is passed on

Article 18 of the Civil Code, quoted on the network's birth page, says a child is French when at least one parent is. France also applies a double jus soli: someone born in France to a parent who was also born there is French, even if both parents are foreigners.

The line has a limit. Under article 30-3, a person who lives abroad, whose ancestors through whom the nationality passes have stayed settled abroad for more than fifty years, and who has not kept the possession of French status, cannot rely on filiation.

The French Embassy in Australia's nationality page explains it, and adds that until 1973 voluntarily acquiring another nationality could make a French citizen lose French nationality.

Proving it

Sometimes the birth certificate is enough: if you were born in France to a parent born there, if you acquired nationality by decree or declaration, or if the certificate carries a nationality mention. Otherwise the proof is a certificate of French nationality (CNF).

The CNF comes from a court, not from a consulate. If you were born and live abroad, the request goes by mail to the Paris judicial court, nationality department, and a refusal can be appealed within six months, with a lawyer.

The network says plainly that its consulates cannot help you build the file or forward it.

Next steps once it is established

A French parent can have a child's US birth transcribed in the French registers, which later makes passport and ID card applications simpler; that is covered in the birth registration guide.

Once your nationality is proven, the passport and the Registre are the usual next steps, and a declaration of loss is possible within a year of acquiring another nationality if you want to renounce.

Official sources: Nationalité française; Ambassade de France en Australie, nationalité française (désuétude, art. 30-3 du code civil); Service-Public.fr, certificat de nationalité française; Naissance.

Details checked against the official pages on October 6, 2026.