If you have not registered your marriage, can your child have foreign nationality?

As prescribed at Clause 2 Article 16 Law on Vietnamese Nationality, the child's nationality is determined as follows:

[....] 2. A child either of whose parents is a Vietnamese citizen at the time of his/her birth and the other is a foreign national has the Vietnamese nationality if so agreed in writing by his/her parents at the time of birth registration. In case a child is born in the Vietnamese territory but his/her parents fail to reach an agreement on the selection of his/her nationality, the child has Vietnamese nationality.

At the same time, Clause 1, Article 36 Law on Civil Status regulations:

1. Birth registrants shall submit the papers specified in Clause 1, Article 16 of this Law to the civil status registration agency. In case either parent is or both parents are foreigner(s), a document on the agreement of the parents on the selection of citizenship for their child.

If the parents choose a foreign citizenship for their child, their agreement document must contain certification of a competent foreign state agency of which they are citizens.

Therefore, children can have foreign nationality when their parents have not registered their marriage on the condition that the parents do written agreement about choosing nationality for your child. However, because the child's parents have not yet registered their marriage, paternity procedures must be carried out to be able to register the child's birth and choose the child's nationality.