Land divisions, in decreasing size, using a townland in South County Dublin to illustrate. Quicklinks :  Province  County  Barony  Parish  Townland

Province 4 The largest Land Divisions in Ireland are the four Provinces. These are Leinster, Munster, Connacht and Ulster, and cover areas in the East, South, West and North of the Island of Ireland respectively.
County 32 There are 32 counties on the Island of Ireland, 12 in the Province of Leinster, 6 in Munster, 5 in Connacht and 9 in Ulster.

Establishing the various counties started in the 12th Century and the last to be created was Co. Wicklow, being established in the early 1600s from parts of counties Dublin, Carlow and Wexford.
County Dublin Highlighted.

26 counties are now in the Republic of Ireland including all of Leinster, Munster, Connaught and three of the counties of Ulster, namely Donegal, Cavan & Monaghan. The remaining 6 counties of Ulster (Antrim, Armagh, Down, Fermanagh, Derry/Londonderry, and Tyrone), are part of the United Kingdom.
Barony ~370 There are about 330 Baronies in Ireland, 9 of which cover parts of County Dublin as shown in the diagram to the right.

These are : Balrothery East, Balrothery West, Nethercross, Coolock, Castleknock, Dublin (city), Newcastle, Uppercross and Rathdown(Highlighted).

Note : The barony of Rathdown also covers part of North Co. Wicklow. The section in Co Dublin is sometimes referred to as a half-Barony.
Civil Parish ~2,570 There are nearly 2,600 civil parishes in Ireland, and 16 in the Barony of Rathdown in Co. Dublin, as shown in the example to the right. Civil parishes are based on areas of pre-reformation churchs and Monasteries.

These civil parishes are : Booterstown, Dalkey, Donnybrook, Kilgobbin, Kill, Killiney, Kilmacud, Kiltiernan, Monkstown, Oldconnaught, Rathfarnham, Rathmichael, Stillorgan, Taney(Highlighted), Tully and Whitechurch.
Townland ~64,000 There are just over 64,000 townlands in Ireland and 19 in the civil parish of Taney as depicted in the diagram to the right.

These townlands are : Balally, Ballinteer, Callary/Mountmerrion, Churchtown Lower, Churchtown Upper, Dundrum Town, Drummartin, Dundrum, Farranboley, Friarland, Kingstown, Mountanville, Mountmerrion South, Owenstown/Trimleston, Rathmines Great, Rathmines Little, Roebuck, Tiknock, and Windy Harbour/Windy Arbour.
    The full designation of the example townland would be Drummartin townland, Taney Civil Parish, Rathdown Barony, County Dublin, although in practice the Barony is not usually included.  

> The numbers of baronies, and parishes are approximate, as some occupy more than area, e.g. a townland can extend into more than one Civil parish, a Barony into more than one county etc.
> Note that barony, parish, and townland names are not always unique, e.g. there are at least two baronies named Bantry, one in Cork the other in Wexford, several civil parishes named Aglish, in counties Kerry, Kilkenny, Mayo etc, and a number of townland names also appear a number of times in different locations around Ireland for example : Newtown (over 170 occurrences), Milltown (80), Killeen (74), Tully (60), Castletown (54), Dromore (48).etc
>Townlands are still in existance, and are currently used as part of postal addresses in rural areas.