Open-air market on Market Street
Eamhain Mhacha (or Navan Fort), at the western edge of Armagh, is believed to have been an ancient pagan ritual or ceremonial site. According to Irish mythology it was one of the great royal sites of Gaelic Ireland and the capital of Ulster. It appears to have been largely abandoned after the 1st century. In the 3rd century, a ditch and bank was dug around the top of Cathedral Hill, the heart of what is now Armagh. Its circular shape matches the modern street layout. Evidence suggests that it was a pagan sanctuary and the successor to Navan. Like Navan, it too was named after the goddess Macha – Ard Mhacha means "Macha's height". This name was later anglicised as Ardmagh, which eventually became Armagh.
After Christianity spread to Ireland, the pagan sanctuary was converted into a Christian one, and Armagh became the site of an important church and monastery. According to tradition, Saint Patrick founded his main church there in the year 457, and it eventually became the "ecclesiastical capital" of Ireland. Saint Patrick was said to have decreed that only those educated in Armagh could spread the gospel. According to the Annals of the Four Masters:
Ard Mhacha was founded by Saint Patrick, it having been granted to him by Daire, son of Finnchadh, son of Eoghan, son of Niallan. Twelve men were appointed by him for building the town. He ordered them, in the first place, to erect an archbishop's city there, and a church for monks, for nuns, and for the other orders in general, for he perceived that it would be the head and chief of the churches of Ireland in general.
In 839 and 869, the monastery in Armagh was raided by Vikings. As with similar raids, their goal was to acquire valuables such as silver, which could often be found in churches and monasteries.
The Book of Armagh came from the monastery. It is a 9th-century Irish manuscript now held by Trinity College Library in Dublin (ms 52). It contains some of the oldest surviving specimens of Old Irish.
Brian Boru is believed to be buried in the graveyard of the St. Patrick's Church of Ireland cathedral. After having conquered the island during the 990s, he became High King of Ireland in 1002, until his death in 1014.
In 1189, John de Courcy, a Norman knight who had invaded Ulster in 1177, plundered Armagh.
Armagh has been an educational centre since the time of Saint Patrick, and thus it has been referred to as "the city of saints and scholars". The educational tradition continued with the foundation of the Royal School in 1608, St Patrick's College in 1834 and the Armagh Observatory in 1790. The Observatory was part of Archbishop Lord Rokeby's plan to have a university in the city. This ambition was finally fulfilled, albeit briefly, in the 1990s when Queen's University of Belfast opened an outreach centre in the former hospital building.
Three brothers from Armagh died at the Battle of the Somme during World War I. None of the three has a known grave and all are commemorated on the Thiepval Memorial to the Missing of the Somme. A fourth brother was wounded in the same attack.
On 14 January 1921, during the Irish War of Independence, a Royal Irish Constabulary (RIC) sergeant was assassinated by the Irish Republican Army (IRA) in Armagh. He was attacked with a grenade as he walked along Market Street and later died of his wounds. On 4 September 1921, republican leaders Michael Collins and Eoin O'Duffy addressed a large meeting in Armagh, which was attended by up to 10,000 people.
During the Troubles in Armagh, the violence was substantial enough for the city to be referred to by some as "Murder Mile". Over the span of 36 years the city seen 84 deaths in the Troubles, including those of a number of people from the city who lost their lives elsewhere in Troubles-related incidents.