Portugal - Passport & Nationality - Portuguese Citizenship by Marriage
You can acquire Portuguese citizenship through marriage. You become eligible after three years of being married to a Portuguese citizen or three years of legally recognized cohabitation. There is no requirement to have had any prior period of residence in Portugal although the applicant is required to provide documents proving an effective connection to the Portuguese community.
If you divorce or separate at a later date, your Portuguese citizenship will not be revoked. However, if you have divorced or separated, you cannot apply for citizenship of the basis of your previous marriage to a Portuguese citizen.
Portugal is a member of the European Union. As a result, a Portuguse passport holder can live and work in any of the EU member states (including Ireland). Subject to what is written above, Dual Nationality (the right to hold a nother nationality) is allowed.