Where to overnight between Dublin and Dingle with visit to Cashel

Have done that drive. Answer is no you don’t need to overnight in Cashel but could if you wanted.

2 hours Dublin to Cashel , 1.5 hour in Cashel, back in car. Cashel to Dingle about 3 hours.

Then again I live in LA where everything is a slog.

I assume you will be coming from far away when you arrive in Ireland. If so, please do not just jump in a car and drive off - on arrival most folks are exhausted and in no condition to be behind the wheel. Also, if your flight home from Ireland (or onward) departs from Dublin, then skip Dublin on arrival - because you need to spend your last night there anyway (so you don't miss your flight). It's more efficient (and safe) to "do" Dublin at the end of your trip, and skip it at the beginning (to save time and be more efficient).

Instead, get off the plane, and take the train or a bus ("coach") to your next destination beyond Dublin - in your case, maybe Limerick or somewhere else near Cashel. Spend your first night there. Get up the next morning, feeling refreshed and in a better condition to drive. Pick up your car and off you go. When you're ready to head back to Dublin, drop your car (pick a location that has both a rail connection and a car rental agency where you can drop your car) and take the rain back to Dublin.

The Dingle area is my favorite! - it's a very long drive from Dublin though a full day really. The first half will be on an M road which is Ireland's version of a freeway, but there are still roundabouts,etc., where you have to slow down. Depends how much you like driving and your experience driving on the other side of the road. There are also N roads (medium) and R roads, which are the smallest and are sometimes one lane wide.

i found driving in Ireland tiring due to the extra work. So i would vote for an overnight in Cashel if you want to see it, though that means you would have 2 days of multi-hour driving. If it was me and i had it to do over again, i would have done a flight from Dublin to Kerry and rented a car from there. Ireland gets more scenic the farther west you go (IMO).

Thank you everyone so far. Yes we will be staying the first day of arrival in Malahide to sleep and avoid driving into Dublin, or anywhere really, on the “wrong” side of the road while sleep deprived. Here is my tentative itinerary, appreciate any feedbacks:

Day 1: Arrive in Dublin in am. Rental car, drive to Malahide and overnight in Malahide
Day 2: Malahide to Cashel. Rock of Cashel. Overnight in Cashel
Day 3: Cashel to Dingle. Overnight in Dingle
Day 4: Dingle Slea Head Drive. Overnight in Dingle
Day 5: Dingle to Kilkee via Shannon ferry. Overnight in Kilkee
Day 6: Cliffs of Moher. The Burren. Overnight in Galway
Day 7: Galway to Dublin. Overnight in Dublin
Day 8: Dublin
Day 9: Flight home

As David mentions— driving in Ireland comes as a real surprise to a lot of Americans because driving on the opposite side of the road combined with some very narrow roads is often too much for the uninitiated. You often get squeezed in by the stone walls commonly used for fencing on both roadsides and the oncoming traffic is often other tourist-drivers who also are not used to navigating roads quite like what you’ll find in Ireland. The stone walls are unforgiving and that’s a major reason why auto insurance through credit cards that might cover you in many other countries, will not cover you in Ireland. Scraped car sides, broken side mirrors and collisions are quite common among visitors.
A post in the last few months from an American told how he picked up a rental car in Dublin, drove out of the parking lot and within 5 minutes he wrecked the car crossing a narrow bridge that had stone walls on both sides. He actually totaled the car.
Add jet lag to the mix and you have a strong possibility of things not going well when driving on your first day in Ireland.
You might overnight in Kilkenny which is a great town in its own right. Kilkenny is 38 miles from Cashel.
EDIT: I see now that you’ll be staying in Malahide following your arrival. Good plan.

Slainte Mhath!

Consider your plan...

Arrive in Dublin in am. Rental car, drive to Malahide and overnight in Malahide

While Malahide is just a stone's throw from the airport, your plan still has you coming off your flight, renting a car, jumping in, and driving away. I'd grant that driving the short distance to Malahide on your arrival day is less dangerous than driving across Ireland on your arrival day, but it's still dangerous, and it does not take a long time to make a mistake. Granted, you will only be exposed to the danger for a short time, but it's still a risk.

(FWIW, once I was waiting to rent a car in Salisbury, England. The American couple in line ahead of us took their keys, jumped in the car, and pulled away from the rental lot as if they didn't have a care in the world. They got less than 100 meters down the street before they had a head-on collision and totaled the car - we heard the loud crash while we were filling out our paperwork, everyone jumped up and ran outside to see the crash site.)

The point being that your first few minutes driving in any foreign country are the most dangerous. I have experienced this myself, after arrival in Saporro, Japan, I rented a car and for a moment started to drive onto a freeway - going the wrong direction, opposite traffic. My wife screamed, I corrected my error quickly, and made a hasty 180. Luckily there was no oncoming traffic so I got away with it, but "muscle memory" is a real thing - and we are all especially vulnerable to it and other dangers of exhaustion, when sleep-deprived and coming off a long flight.

I'd also gently suggest that it looks to me like you are needlessly wasting your arrival day - on a trip where you have precious few days to utilize. It's true that you should probably not expect too much of yourself on your arrival day. But remember: no matter when you do it (and regardless of your mental clarity at the time), it's still going to take you almost a full day to cross Ireland from Dublin to anyplace near Dingle, and you are going to have to spend some time doing that. So for efficiency, I'd push on after arrival as far towards my goal as I could. You may be groggy, maybe will be fast asleep on the way. But you can do that - without risking disaster - as long as you are not the one driving. Like on a train or a bus.

Another thing to consider: We pay for car rentals by the day. You are planning to arrive in Ireland, rent a car, drive it for maybe 10 minutes, then you will park it and go to sleep. Dangers and inefficiencies aside, that does not seem like a good use of your rental car money. You don't really need a car until you're in a reasonable condition to actually drive it, so why not take a taxi or find some other way to your first night's lodging (which could be half-way across Ireland, just sayin'...). After you wake up the next day, THEN rent your car and drive off.

There are buses that leave right from the Dublin airport. There are trains that leave from Dublin's city station, not that far from the airport. Either of those could get you far to the southwest, where it seems you're really headed.

Or, even better, consider this: Reverse the direction of your trip (from clockwise to counter-clockwise). From the airport, just catch a bus to Galway. Sleep there your first night. Rent your car when you're ready to move south from Galway. Do Dingle and the southwest. Drop your car where and when you're done with it, catch a train back to Dublin and sleep there the last night before you fly out. That would be a much more time-efficient way to go (I did exactly that, and managed a LOT of the good bits of Ireland in a short time).

Hope some of this helps.

Galway as destination #1 on arrival is what I was also going to recommend. ( David, I think, is telepathic) There are direct express buses from DUB airport to five-star *****Galway. Then, you can start the car rental when you leave Galway and drive to Cashel. You can return the car before your time in Dublin.

That's exactly what we did - going counter-clockwise to connect these dots on the map worked great (as recommended by several people here).

Bus from the airport to Galway, excellent sleeping conditions (cheap, just steps from the airport terminal, roomy seats, big panoramic windows, warm and cozy, free wifi...zzzzzz). Wake up in Galway, check in to the B&B, out for a refreshing walk before dinner, then deep sleep. The trip begins the next morning.