If you were born outside Ireland but one or both of your parents was an Irish Citizen at the time of your birth – then it is possible for you to get Irish Citizenship.
( See Irish Citizenship through Naturalisation if you have no Irish ancestors)
Your parent(s) would be an Irish Citizen if one or both of their parents were born in Ireland. So – to summarize – if one or more of your grandparents were born in Ireland it is possible for you to claim Irish Citizenship even if you nor any of your parents were born in Ireland . You can claim Irish citizenship even if you live outside Ireland.
You will first have to get your birth registered in the Register of Foreign Births which is kept by the Department of Foreign Affairs in Dublin. You will need to get an application form from them – Their address is Dublin 2, Dublin.
You will need quite a lot of documentation to go along with your application to register .
You will need The Applicant’s Birth Certificate , Marriage Certificate if applicable and copy of current passport or identity document.
You also need to select one parent – who is linked to the Irish born grandparent – and for this parent you will also need Birth Certificate, Marriage Certificate and a copy of their passport or other identity document. If the parent is not living you will need a death certificate.
Finally – for the grandparent that was born in Ireland – you will need the Irish birth certificate . marriage certificate and if living – a copy of their passport or identity document – otherwise a death certificate.
All certificates must be originals or certified copies from the originating office. Photocopies are not accepted.
Two passport size photos are required and these have to be authorised by a witness such as a priest, doctor, head teacher, lawyer or policeman who knows the applicant.
If the person claiming citizenship is under 18 – then the parent must sign the application and also provide 2 photos signed on the back by the witness.
The form also has to be witnessed.
There is a fee for the registration of foreign births – the fee depends on your country of residence . You get a certificate of proof which you will need if you want apply for an Irish passport
Applications for Irish citizenship must be made to the Irish Embassy in the country you are residing. In Ireland you apply to the Consular Services Section , Dept of Foreign Affairs.
More details here about how UK Residents can get an Irish Passport