Ireland itinerary for 16 days. I would welcome helpful critique.

That is an intensive itinerary and if you are wanting to actually ‘do’ all the things on the list rather than just a quick look at the outside.

Day 4 - It is going to take about 3 hours to drive from Kilkenny to Kinsale. Visiting Kilkenny Castle and Rothe House is going to take up the full morning. Cashel Castle - do you mean Rock of Cashel? You need to allow about 90 minutes to see the castle PLUS time to find somewhere to park and get to the castle... so you are effectively talking about 2 hours for Cashel. It is going to be late afternoon by the time you reach Kinslae. I can’t see you getting the fort done that afternoon...

Day 10 This is going to take 4+ hours to drive. Bunratty Castle and Folk Park - you could easily spend a full day there as there is so much to see and enjoy...

Day 11 and 12 - this is more like 4 days than 2

Day 13 &14 Again this is more like 4-5 days. The plans for the first day are completely unrealistic It’s going to take 4+ hours just to drive to Donegal, and more like 6 if you do the detour to Achill Island (and that’s not seeing anything of the island either....) The Ben Bulben walk is going to be 90 minutes plus.

Day 15 - Forget trying to do Glenveagh NP in the morning. It’s going to take the full day to drive to Belfast with Dunluce Castle, Giant’s Causeway and the Antrim coast.

Don't underestimate driving times in Ireland. Thety will be slow and it will take a lot longer to cover the distances than you might expect. 2 nights in a place only effectively gives a full day and a bit as you need to allow for time to drive there.

I would recommend that you re-read RS' advice on itinerary planning. You've done a great job of listing all the things you want to see and do. Now go back and figure out how much time is involved in each place/activity. Wasleys has provided a start on this process. I think you'll quickly see that you don't have time to see and do everything on your list. Next step, prioritize your sights and activities. You don't offer any guidance for this, but I'd guess you're looking to enjoy natural beauty and castles. If I am correct, you might look at flying into Shannon and out of Dublin and skipping Dublin entirely. This would gain you 3 days or more, which would make the trip less frantic, but I would still cut something.

Thank you for your quick replies!

Day 4 would it be better to do Kilkenny AM, Rock of Cashel, Blarney Castle, overnight in Blarney

Day 5 Kinsale in the AM, Mizen Head in the PM , evening in Kenmare
or is this still too much?

Day 11-12 were all of the things to see/do that we are interested in. Definitely want to do the Hawk Walk at Ashford Castle.
I know it will not be possible to see everything :(. Do you think it would be best to stay both nights in one place?

Day 13-14 same. It's very difficult to choose when everything looks beautiful. I'm thinking to skip Archil Island and Downpatrick Head as they add a lot of driving time.

Day 15 go to Sleive Leigh, Silver Strand and this general area and in the PM drive to Glenveagh NP, stay in Letterkenny

Day 16 Dunluce Castle, Giant's Causeway, Atrium Coast, overnight Belfast area

We are interested in natural beauty, castles and a few pubs too.

Thanks again!

A great place to stay in Donegal is Killybegs, which offers good access (by both land and sea) to the Slieve League.
For the Antrim Coast sights, Bushmills is a good place to stay, but you'll need to check out early to make it back to the Dublin Airport in time to drop the car, check in, etc.

Day 4 would it be better to do Kilkenny AM, Rock of Cashel, Blarney Castle, overnight in Blarney

No. The driving time is not much less than heading to Kinsale. Blarney castle website recommends allowing three hours for a visit. Last entry time is 5pm. I suppose you might manage this if all you want to do is kiss the Blarney stone...

Day 5 Kinsale in the AM, Mizen Head in the PM , evening in Kenmare

A lot may depend on how long you intend to spend in Kinsale. You need to allow 5 hours to drive from Kinsale to Mizen Head and then to Kenmare...

I am exhausted just reading this. Have you ever driven on the left on winding hard to pass roads?
Everything is going to take a lot longer than you realize. I would spend min two nights but if possible three nights at a location. You really need to cut out items or most of your trip will be in a car. But hey it’s your vacation.

My only real contribution is to listen to wasleys. You haven’t accurately accounted for driving times and touring time for a number of days. I feel like your number of days could get you through the Ireland portion of your itinerary if you leave off Northern Ireland.

We did a 12-day adventure tour with a similar route. It didn't include Dublin (we did that on our own), but I think you could do this (or most of it) in your 16 days.

My's husband's great-grandmother is from Clifden, so of course that is my choice! We stayed at Abbeyglen Castle Hotel. It was a little quirky, but we especially liked the piano music in the bar in the evening. We stayed at the Waterfront House in Enniscrone. The beach just across the street was magnificent.