Ireland do I need a car?

Without knowing what you want to do or where you want to go it's hard to answer whether you need a car. Depending on where you base yourself you might be able to rely on organized day trips. If you do rent a car you might want to consider whether there will be a one-way drop-off fee when departing from Dublin. To avoid a drop fee you might have to go with one of the bigger airport based agencies.

Hi from Wisconsin,
Well, Shannon airport is in a cow pasture...OK, that is a bit of an exaggeration. So you would need to take a bus to Ennis or some where else if you wanted to see a nice medieval place. I would rent a car at the airport. It has been a while since I was in Ireland, but they have some off brand names that are fine and inexpensive, things like Bill Reilly's Auto, or Treaty Auto rental.

four days...I am such a bummer. Does that mean you flew in from the US, so you will be tired the first day. And is the fourth day the day you fly out? Of are there six days involved. The day you arrive, then four days to tour, and then the day you exit Ireland.

It sounds like such a good idea to land in one spot and fly out from the other. If you only have two true days to tour, get the car and start heading to Dublin. You might plan your touring as a nice way to get from the west coast to Dublin. If you have four days...you could easily head north from Shannon, go north of Galway into Connemara. Or go south from Shannon and see the Beara Pennisula and go along the southern coast making sure to get to Cashel and Glendalough.

wayne iNWI

You wouldn’t need a car if you could get yourself to Galway by public transit. You could base yourself there and take guided day trips to see the sight then take the train to Dublin. There are a lot of options for day trips around Galway so with your limited time this might be your best option. Even if you had a car it still might be your best option. Cliffs of Moher, Burren, Connemara, Aran Islands are all in the Galway area.