Born between 1 January 1925 and 1 December 1950
If you were born before 1 January 1925, you became Norwegian at birth if your father or your mother were Norwegian when you were born, and your parents were married. You also became Norwegian at birth if your mother was Norwegian, but not married, when you were born.
If only your father was Norwegian and your parents married after you were born, but before you reached the age of 18, you became Norwegian at the point in time when your parents became married.
Documentation
You must have a birth certificate and be able to document that at least one of your parents was Norwegian when you were born.
If your father or if both your parents were Norwegian you must submit your parents’ marriage certificate.
If only your mother was Norwegian you must submit documentation that shows that your parents were not married when you were born.
Applicable law
"The Norwegian Nationality Act of 8 August 1924, no 3".