O’Hanlon is born in 1620 near Poyntzpass, County Armagh, in what is now Northern Ireland, the son of Loughlin O’Hanlon, rightful heir to Tandragee Castle. As a young man he is sent for a “proper” education in England and later works as a footman to Sir George Acheson of Markethill, but is dismissed for stealing horses. After the Irish Rebellion of 1641, he joins the Irish Catholic rebel forces. He serves under Owen Roe O’Neill at the Irish victory at the Battle of Benburb in 1646 but flees to France after the defeat of the Irish Confederation in the Cromwellian conquest of Ireland. O’Hanlon’s family lands are confiscated under the Act for the Settlement of Ireland 1652.
O’Hanlon spends several years in exile as an officer with the French army and is awarded the title of Count of the French Empire. He returns to Ireland around 1660, after the Restoration of King Charles II of England. After realizing there will be no restitution of his family’s lands, he takes to the hills around Slieve Gullion and becomes a notorious highwayman.
Although O’Hanlon is often compared to a real-life Robin Hood, the truth is more complex. Protestant landlords, militia officers, and even Anglican and Catholic priests work as informal members of the O’Hanlon gang, giving him information and scouting sites for him to rob. He also forces the landlords and merchants of northern Ireland to pay protection money. It is stated that the criminal activities of O’Hanlon are bringing in more money than the King’s revenue collectors.
In 1674 the colonial authorities in Dublin put a price on O’Hanlon’s head with posters advertising for his capture, dead or alive. The Anglo-Irish landowner Henry St. John, who had been granted the traditional lands of the O’Hanlon clan, receives O’Hanlon’s undying hatred when he begins evicting his clansmen in large numbers. St. John responds by waging a private war against the O’Hanlon Gang. The loss of his 19-year-old son while pursuing O’Hanlon only makes Henry St. John increasingly brutal toward anyone suspected of aiding Redmond O’Hanlon. On September 9, 1679, St. John is riding on his estate with a manservant and the Reverend Lawrence Power, the Church of Ireland Rector of Tandragee. A party of O’Hanlon’s associates ride into view and seize him, warning that he would be killed if a rescue is attempted. Then, a group of the family’s retainers ride into view and open fire on the kidnappers. As a result, Henry St. John receives two pistol balls in the forehead.
At the landlord’s funeral, an outraged Reverend Power denounces the outlaws and the landowners who do business with them. Outraged, James Butler, 1st Duke of Ormond, the Lord Deputy of Ireland, orders the assassination of O’Hanlon.
Count Redmond O’Hanlon is murdered in his sleep by his foster brother and close associate Art MacCall O’Hanlon at Eight Mile Bridge near Hilltown, County Down on April 25, 1681. Art receives a full pardon and two hundred pounds from the Duke of Ormond for murdering his leader. William Lucas, the militia officer who had recruited Art and arranges the killing, receives a Lieutenant’s commission in the British Army.
As is the custom of the day, there are gruesome displays of his body parts including his head which is placed on a spike over Downpatrick jail. His remains are eventually removed to lie in a family plot in Conwal Parish Church cemetery in Letterkenny, County Donegal, where his parents had fled from Henry St. John. His bones, however, are not left to rest in peace there and his grave is constantly desecrated by the Duke’s supporters. His remains are finally removed by his family and interred in his final secret resting place, somewhere within Lurgan Parish.