The northern region of Ulster was an ancient kingdom, and one of the four historic Provinces of Ireland. The region was mostly annexed by the English Crown during the reign of James I (1603-1625).
In the Middle Ages, the Province of Ulster contained the counties Donegal, Derry, Antrim, Down, Armagh, Cavan, Monaghan, Fermanagh, and Tyrone.
The Province of Ulster is now divided between The Republic of Ireland, and Northern Ireland, which is often referred to as Ulster. Northern Ireland is a political division of the United Kingdom; it is made up of the counties Antrim, Armagh, Down, Fermanagh, Derry, and Tyrone.
The 26 districts present day Northern Ireland are: Antrim, Ards, Armagh, Ballymena, Ballymoney, Bainbidge, Belfast, Carrickfergus, Castlereagh, Coleraine, Cookstown, Craigavon, Down, Dungannon, Fermanagh, Larne, Limavady, Lisburn, Londonderry, Magherafelt, Mourne, Moyle, Newtownabbey, North Down, Omagh, and Strabane.