It is named after its county town, Armagh, which derives from the Irish Ard Mhacha, meaning "Macha's height".

Macha was a sovereignty goddess in Irish mythology and is said to have been buried on a wooded hill around which the town of Armagh grew.

In the north it gives way to flatlands where rolling flats and small hills reach sea level at Lough Neagh.

Despite lying in the east of Ireland, Armagh enjoys an oceanic climate strongly influenced by the Gulf Stream: featuring damp mild winters, and temperate, wet summers.

Overall temperatures rarely drop below freezing during daylight hours, though frost is not infrequent in the months November to February.

The chief Irish clans of the county were descendants of the Collas, the O'Hanlons and Mac Cana, and the Uí Néill, the O'Neills of Fews.

The area around the base of Slieve Gullion near Newry also became home to a large number of the Clan McGuinness as they were dispossessed of hereditary lands held in the County Down.

During the 17th and 18th centuries, County Armagh was a major center of guerrilla warfare, cattle raiding, and brigandage by local Rapparees; including Count Redmond O'Hanlon, Cormacke Raver O'Murphy, and Séamus Mór Mac Murchaidh.

The southern part of the county has been a stronghold of support for the Provisional IRA, earning it the nickname "Bandit Country".

[18] South Armagh is predominantly nationalist, with much of the population being opposed to any form of British presence, especially that of a military nature.

The officer was fatally shot by a sniper as he and a colleague investigated "suspicious activity" at a house nearby when a window was smashed by youths causing the occupant to phone the police.

[29] Government Minister for the Department for Regional Development, Danny Kennedy MLA indicates railway restoration plans of the line from Portadown to Armagh.

[30] Ulsterbus provides the most extensive public transport system within the county, including frequent bus transfers daily from most towns to Belfast.

Northern Ireland Railways/Iarnród Éireann's Enterprise service provides connections to Dublin in little over an hour and Belfast in little over forty minutes, several times daily.