The Battle of Curlew Pass was fought on 15 August 1599 during the campaign of the Earl of Essex in the Nine Years' War, between an English force under Sir Conyers Clifford and a rebel Irish force led by Aodh Ruadh Domhnaill (Red Hugh O'Donnell). The English were ambushed and routed while marching through a pass in the Curlew Mountains, near the town of Boyle, in the west of Ireland. The English forces suffered heavy casualties. Losses by allied Irish forces were not recorded but were probably minimal.



The Nine Years' War, sometimes called Tyrone's Rebellion, took place in Ireland from 1593 to 1603. It was fought between an Irish alliance—led mainly by Hugh O'Neill of Tyrone and Hugh Roe O'Donnell of Tyrconnell—against English rule in Ireland, and was a response to the ongoing Tudor conquest of Ireland. The war was fought in all parts of the country, but mainly in the northern province of Ulster. The Irish alliance won some important early victories, such as the Battle of Clontibret (1595) and the Battle of the Yellow Ford (1598), but the English won a decisive victory against the alliance and their Spanish allies in the siege of Kinsale (1601–02). The war ended with the Treaty of Mellifont (1603). Many of the defeated northern lords left Ireland to seek support for a new uprising in the Flight of the Earls (1607), never to return. This marked the end of Gaelic Ireland and led to the Plantation of Ulster.

The war against O'Neill and his allies was the largest conflict fought by England in the Elizabethan era. At the height of the conflict (1600–1601) more than 18,000 soldiers were fighting in the English army in Ireland. By contrast, the English army assisting the Dutch during the Eighty Years' War was never more than 12,000 strong at any one time.