A passport or national identity card is the only documentation needed by citizens of the other EU member states to enter Ireland. Citizens from non-EU states must have a passport but not a visa for a short-term trip to Ireland.
Travelers from the United States, Canada, Australia and New Zealand are not required to have a visa to enter the country. Citizens of a number of countries from the Middle East, Africa and Central and Eastern Europe are required to hold visas in order to enter Ireland. For further information, you should refer to the Irish Department of Foreign Affairs in Dublin.