Geography of Ireland

Breffny (Breifne):
- Cavan
- West Leitrim
Corca Laoidhe:
- South-west Cork
Dalriada:
- North Antrim
Decies (Déise):
- West Waterford
Desmond (Deasmhumhan):
- Kerry
- Co. Cork.
Iar Connacht:
- West Connacht, mainly Connemara.
Muskerry (Muscraidhe)
- North-west and central Cork.
Oriel (Orghialla): Counties:
- Armagh
- Monaghan
- Parts of south Down
- Parts of Louth
- Parts of Fermanagh
Ormond (Urmhumhan):
- Co. Kilkenny
- North Tipperary
Ossory: The extent of the ancient kingdom of Osraighe was approximately the same as that of the diocese of Ossory, ie. Co.
- Kilkenny and some adjacent areas.
Thomond (Tuathmhumhan): Most of
- Co. Clare with adjacent parts of Counties:
- Limerick
- Tipperary
Tirconnell (Tir Chonaill):
- Co. Donegal.
Tirowen (Tir Eoghain):
- Co. Tyrone
- Adjacent part of Co. Derry

Cenél Conaill: The race name of the
- O'Gallagers
- O'Boyles and other families traditionally descended from Conall Gulban, son of Niall of the Nine Hostages, located in Tirconnell.
Cenél Eoghain: The clan name of the Ó Neills etc. descended from Eoghan, son of the Nine Hostages, located in
- Tyrone
- South Derry
Dál gCais: Otherwise called the Dalcassians; embraces the main septs/clans of
- Thomond
Eoghanacht: The clan name of the descendants of Eoghan, son of Oilioll Olum, to which many of the main families of
- South Munster
Síl Anmchadha: A branch of the Uí Maine.
Síl Muireadhaigh (Silmurray) The clan of the O'Connors and other
- North Connacht septs.
Uí Fiachrach: The northern and more important, ie. Uí Fiachrach Muaidhe, were located in
- North Mayo and Sligo;
- Branch (Aidhne) occupied that part of south Galway covered by the small diocese of Kilmacduagh.
Uí Maine (At one time anglicized Hy Many):
- Mid-Galway
- South Roscommon

Ireland is made up of four provinces, Ulster, Connacht, Leinster, and Munster, which are divided into thirty-two counties. Six counties in the province of Ulster make up the territory of North Ireland.
Province of Connacht: Counties:
- Galway
- Roscommon
- Leitrim
- Sligo
- Mayo
Province of Munster: Counties:
- Clare
- Cork
- Kerry
- Limerick
- Tipperary
- Waterford
Province of Leinster: Counties:
- Carlow
- Dublin
- Kildare
- Kilkenney
- Leix (Laois)
- Longford
- Louth
- Meath
- Offaly
- Westmeath
- Wexford
- Wicklow
Province of Ulster: (Republic of Ireland) Counties:
- Cavan,
- Donegal, and Monaghan.
(North Ireland) Counties: