Many couples marry abroad and provided all the legal rules for marriage in the country where the marriage takes place are complied with the marriage will be recognised as valid in Ireland.
Many couples also divorce abroad; however, the rules in Ireland on the recognition of foreign divorces are far from simple. Certain rules apply for divorces applied for prior to October 1986 and different rules apply after that date. Certain other rules apply between EU Member State (save Denmark) since Brussels 11 bis Reg. No. 2201/2003 came into force from 1st March 2005. The critical rule in the regulation is that when a court application for separation/divorce is properly made in a Member State then the Courts of that country are entitled to hear the case even if the other spouse would prefer the case was dealt with elsewhere.
So if you are an Irish person living abroad or are married to a non-Irish person you should get prompt legal advice otherwise you may end up fighting a divorce case in a foreign court.