Portugal - Passport & Nationality - Portugal Citizenship - Portuguese Ancestry
It is possible to claim Portuguese citizenship a parent (mother of rather) was a Portuguese citizen at the time of your birth, irrespective of where they were born. The relevant parent(s) or grandparent(s) do not need to still be alive.
As of 29 July 2015, those born outside Portugal who have at least one grandparent of Portuguese nationality, are granted Portuguese citizenship by extension immediately.
Portugal is a member of the European Union. As a result, a Portuguese passport holder can live and work in any of the EU member states (including Ireland). Dual Nationality (the right to hold a nother nationality) is allowed.