Armagh comes from the Irish word Ard Macha - Macha's Height, alluding to Queen Macha who supposedly built a fortress on top of a hill. Armagh is also popularly known as "the Orchard County" because of its success in the growth of Bramley Apples. Armagh was ruled over by the O' Neills in medieval Times. In 1795 the Orange Order was founded in Armagh.

Ireland’s spiritual capital for 1,500 years and the seat of both the Protestant and Catholic archbishops, the city of Armagh predates Canterbury as a Christian religious site. Armagh was also the legendary seat of the Celtic kings of Ulster.

Its main town is Armagh, in the middle of the county, although Lurgan at the extreme north-east has a larger population. The counties of Northern Ireland ceased to be administrative entities in the 1970s, with the reorganization of local government.