You are automatically an Irish citizen if one of your parents was an Irish citizen at the time of your birth and was born on the island of Ireland. You don’t need to apply to become an Irish citizen in this case.
You can become an Irish citizen if:
In these cases, you can become an Irish citizen through Foreign Birth Registration.
Once a person is entered onto the Foreign Births Register they are an Irish citizen and entitled to apply for an Irish passport.
To register your birth on the Foreign Births Register, you must:
Send your application to the address printed on top right-hand corner of your application form. This will be either a specified Irish Embassy or Consulate, or a PO Box address in Ireland.
Submit a query regarding Foreign Birth Registration.
If you’re applying for citizenship through naturalisation or have other issues with citizenship, contact the Irish Naturalisation and Immigration Service of the Department of Justice and Equality.