Poor Law Unions (or Superintendant Registrar's Districts) were the areas of administration for poor relief established under the Poor Relief (Ireland) Act, 1838. They became Superintendant Registrars' Districts at the end of the 19th century.
Poor Law Unions A-Z
Because these areas centred on large market towns to a radius of about 10 miles, they often tended to cross county boundaries.
| Union | County/Counties |
| Armagh | Armagh |
| Ballycastle | Antrim |
| Ballymena | Antrim |
| Ballymoney | Antrim |
| Ballyshannon | Fermanagh, Donegal and Leitrim |
| Banbridge | Armagh and Down |
| Belfast | Antrim and Down |
| Castleblayney | Armagh and Monaghan |
| Castlederg | Tyrone |
| Clogher | Tyrone |
| Clones | Fermanagh and Monaghan |
| Coleraine | Derry~Londonderry |
| Cookstown | Tyrone |
| Downpatrick | Down |
| Dungannon | Tyrone |
| Enniskillen | Fermanagh and Cavan |
| Irvinestown | Fermanagh and Tyrone |
| Kilkeel | Down |
| Larne | Antrim |
| Limavady | Derry~Londonderry |
| Lisburn | Antrim and Down |
| Lisnaskea | Fermanagh |
| Derry~Londonderry | Derry~Londonderry and Donegal |
| Lurgan | Antrim, Armagh and Down |
| Magherafelt | Derry~Londonderry |
| Newry | Armagh and Down |
| Newtownards | Down |
| Omagh | Tyrone |
| Strabane | Tyrone and Donegal |