Ulster is one of the four historical provinces which make up the island of Ireland. The others are Leinster, Munster and Connacht.
There are nine counties in Ulster. Three of them are in the Republic of Ireland:
The other six counties make up all of Northern Ireland, which is part of the United Kingdom:
Because most of Ulster is in Northern Ireland, the name "Ulster" is also sometimes used to mean Northern Ireland, even though Northern Ireland is only part of Ulster. This is called totum pro parte in Latin which means "the whole for a part".
County Galway (Galway City) · County Leitrim · County Mayo · County Roscommon · County Sligo
County Clare · County Cork (Cork City) · County Kerry · County Limerick (Limerick City) · County Tipperary (North Tipperary • South Tipperary) · County Waterford (Waterford City)
County Carlow · County Dublin (Dublin City • County Dun Laoghaire-Rathdown • County Fingal • County South Dublin) · County Kildare · County Kilkenny · County Laois · County Longford · County Louth · County Meath · County Offaly · County Westmeath · County Wexford · County Wicklow
County Cavan · County Donegal · County Monaghan · County Antrim · County Armagh · County Down · County Fermanagh · County Londonderry · County Tyrone