Everyone entering Ireland must have a valid passport or in the case of European Union Member States, a national identity card. Visas are not required for most European and Eastern European countries. A complete list of countries whose passport holders do not require an entry visa is available from here.
Irish Visa Applications
Citizens of other countries should check with the local Irish representation. The Irish Naturalisation and Immigration Service provide an online visa application facilitaty online visa applications.
Complete information on various visa types can be found here