Birth to an Iranian father creates nationality. There is no unrestricted jus soli, but conditional territorial routes exist (a person born in Iran of foreign parents where one parent was also born in Iran, or a person born in Iran to a foreign father who continues to reside there after age 18).
The foreign wife of an Iranian man becomes Iranian automatically on marriage.
A child of an Iranian father is Iranian by descent regardless of birthplace. Since a 2019 reform, an Iranian mother married to a foreign father may apply for Iranian nationality for her children.
An adult of good character with about five years of residence in Iran may be naturalized subject to Council of Ministers approval; grant is discretionary.