Provinces and Counties in Ireland

Ulaidh – Cúige Uladh – Ulster

Ulaidh is the nominative, Uladh is the genitive. After simple prepositions, dative can be used: in Ultaibh, le hUltaibh.

Counties:

Aontroim – Antrim (gen. Aontroma)

Ard Mhacha – Armagh

an Cabhán – Cavan (gen. an Chabháin)

Doire – Derry

an Dún – Down (gen. an Dúin)

Dún na nGall – Donegal (Tír Chonaill – Tyrconnell)

Fear Manach – Fermanagh

Muineachán – Monaghan (gen. Mhuineacháin)

Tír Eoghain – Tyrone

Laighin – Cúige Laighean – Leinster

Laighin is the nominative, Laighean is the genitive. After simple prepostions, you might see the dative form: i Laighnibh.

Counties:

Áth Cliath – Dublin

Ceatharlach – Carlow (You’d expect this -ach to become -aigh or -aí in the genitive, but the recommended genitive form is Cheatharlach, i.e. with just the first consonant mutated.)

Cill Chainnigh – Kilkenny

Cill Dara – Kildare

Cill Mhantáin – Wicklow

an Iarmhí – Westmeath (gen. na hIarmhí)

Laois (gen. Laoise)

Loch Garman – Wexford. Actually, the form is etymologically speaking Loch gCarman, with an eclipsis that isn’t a regular feature of the language anymore (similar fossilized forms are found in an Muileann gCearr ‘Mullingar’, Loch nEathach ‘Lough Neagh’ etc.); Wexfordmen are called Carmanaigh in Irish.

an Longfort – Longford (gen. an Longfoirt; it would make more etymological sense to write it as an Longphort)

Lú – Louth

an Mhí – Meath (gen. na Mí)

Uíbh Fhailí – Offaly

An Mhumhain – Cúige Mumhan (!) – Munster

an Mhumhain, gen. na Mumhan.

Counties:

Ciarraí – Kerry

an Clár – Clare (gen. an Chláir)

Corcaigh – Cork (gen. Chorcaí)

Luimneach – Limerick (gen. Luimnigh)

Port Láirge – Waterford

Tiobraid Árann – Tipperary

Connachta – Cúige Chonnacht – Connacht

Connachta, gen. Chonnacht, dative Connachtaibh (i gConnachtaibh)

Counties:

Gaillimh – Galway (genitive: na Gaillimhe; in Munster Irish, “in Galway” is “sa Ghaillimh” rather than “i nGaillimh“)

Liatroim – Leitrim (genitive: Liatroma)

Maigh Eo – Mayo

Ros Comáin – Roscommon

Sligeach – Sligo (genitive: Shligigh)