Flights, cars, and trains - Northern Ireland and Ireland

Renting a car in the UK (Northern Ireland) and returning it in Ireland is more hassle than it's worth it is worth just take the many cross border train or buses to Ireland from NI

Also why would the train and bus option to the north coast of Northern Ireland be not attractive Northern Ireland is a small country it takes an hour from Belfast to the north coast on the train why is that not a viable option

Paulscales - thanks for the thoughts. I am definitely open to the train/bus option to explore the coast. It just seems it might be easier to do with a car, particularly if I want to do more than just Giant's Causeway. The (seemingly lesser traveled?) Antrim Coast & Glens looks beautiful. I suppose there's probably some sort of option to take a train to Coleraine, transfer to the bus and hop on/off as desired to explore sites, then possibly transfer to a different bus if needed to move down the Antrim Coast toward Larne (I think there is a train back to Belfast from there). Seems like it'd be a long day, but I suppose we wouldn't be tired from driving. We do love using public transportation when we can while traveling, so perhaps I should look into it a bit more.

There's no particular hassle involved in renting a car in NI and returning it in the Republic since there are no border controls between the two countries so crossing from one to the other is really pretty seamless. The problem is the one-way drop fee which is currently about 250 Euros based on a quick look at the AutoEurope website ( the preferred source for car rentals for many of us here), so that's likely not an attractive option for you.
Having a car for at least one day would be my preferred way of seeing the Antrim Coast, the Causeway Coast, and other sites in the north - including extended excursions over to Donegal and/or Connemara if so inclined. You really can't beat the freedom of movement that having your own car will provide. That said, your idea of renting one for your time in the north and then returning it before hopping on the bus or train to Dublin is probably your easiest and most cost-effective option.
The rental car concessions at Dublin airport have the largest fleet of rentals in the country and thus a greater chance of getting exactly the type of vehicle you want - including one with automatic transmission which I strongly suggest if you'll be first-time drivers in LH traffic.
Might be easiest to catch the express bus from Belfast directly to Dublin airport - the train will take you into the city from where you'd have to double back. Know too that the rental car lot isn't physically located at the airport but about a half mile away along Swords Road, so you'll need to taxi or shuttle to get there. It's not as much of a hassle as it sounds since it's a straight shot from the rental car lot onto the M50 motorway to be on your way.
Might also add that there are 2 cheap flights per day on RyanAir between Dublin and the Kerry airport near Killarney. If you're interested in seeing Dingle and the ROK catching one of those and then renting your car at Kerry would save you a bit of driving.

Thanks for the advice, Robert.

Yes, trying to avoid a fee like $250 if possible! If renting a car, we will either begin/end in Dublin, or do two separate rentals. Great tip about taking the bus from Belfast to Dublin Airport, if picking up a rental there for the Ireland portion. I had only though to take the train, which would then require us to rent a car in central Dublin (or go back out to the airport). Makes so much more sense to pick up the car at the airport, avoid chaotic city driving, and head right out to the next adventure.

Would love to do Dingle or Ring of Kerry, but may save that for another trip. I have a lot of ancestors from Cos. Carlow and Waterford (in addition to Tyrone and Cavan in the north), so am trying to prioritize visiting those places (even if they're less popular/touristy) on this trip. Also am trying to avoid spending 12 days driving!

I think the third option you listed in your original post makes the most sense. Fly into Belfast, sightsee there, rent a car to explore the Antrim Coast and elsewhere in the north, return it in Belfast and take either the train or Aircoach to Dublin. Aircoach can take you straight to DUB where you should have the best selection of cars. Then drive wherever you want in the south and drop the car before finishing in Dublin. Two rentals for two countries, no dropoff fee. As someone else noted, you can drive either car into either country as long as you don't return it in the "wrong" country.

I can't figure out what your total timeframe is for this trip, but you may be at risk of trying to see too much in too little time. Driving in Ireland can be fast on motorways but slow on narrow secondary roads with lots of scenery to admire. I agree that it's a bad idea to drive after an overnight flight, and you won't want a car in Belfast or Dublin themselves.

Thanks for the advice, Dick. The trip will start with 4 nights in Belfast. I understand this is longer than most spend, but I will be there for a conference, so essentially using that as a reason to finally get to Ireland! And will have some free time up there to do the coastal drive, city exploring, etc.

The duration of the rest of the trip is a bit flexible -- likely 6 additional nights. Since we will get a solid city fix in Belfast, I'm fine with only spending 2-3 nights in Dublin (at the end of the trip) -- I assume if I ever travel to Ireland again, I'll find myself flying into or out of Dublin, with additional opportunities to explore the city then. So, that leaves us with 3-4 additional nights.

Belfast is not in Ireland it is in Northern Ireland which is in the United Kingdom
whilst Northern Ireland is on the geographical land mass of the Island of Ireland
"Eire/Ireland" is the official name of the 26 counties governed from Dublin if referring to the Island say "the Island of Ireland"
as saying "Ireland" alone refers to the republic and alot of people in Northern Ireland will soon tell you that youre not in Ireland but Northern Ireland

If the area around Carlow and Waterford is your primary focus you can save yourselves a few euros by taking the bus or train from Dublin to Waterford city and then renting a car there for 2 or 3 days while you explore a particularly pretty part of the country on your roots quest.
With rental car rates still at historically high levels - especially once you factor in automatic transmission and the insurance cover - you're well advised to minimize the time that you actually need one.
Picking up your rental at Dublin airport might be cheaper over all, and would have the advantage of allowing a drive thru the Wicklow mountains and a stop at the Glendalough monastic site on your way south. If that's not important to you then using public transportation to get to Waterford and renting your car there might simplify your logistics a bit.