The Irish Catholic Confederation was a period of Irish Catholic self-government that lasted from 1642 to 1652, during the Eleven Years' War. In the aftermath of the 1641 rebellion by Catholic gentry and military officers seeking an end to anti-Catholic discrimination and the return of confiscated Catholic lands, Bishop Nicholas French and lawyer Nicholas Plunkett recruited Irish Catholic nobles to contribute their armed forces to a Confederation formed on 17 March 1642. The Confederation, which included Catholics of Gaelic and Norman descent, continued to profess loyalty to King Charles I of England while seeking greater self-governance and a rollback of the Plantation of Ulster. Confederate armies fought Royalists, Parliamentarians, Ulster Protestant militia, and Scots Covenanters in the Irish Confederate Wars, but King Charles I negotiated a ceasefire with the Confederates in September 1643 in exchange for their help against his Calvinist rivals in Scotland and England. The Confederates sent an army to Scotland in 1644 to help Royalists there, while they continued to fight the Parliamentarians in Ireland and defeated the Covenanters at the Battle of Benburb. In 1647, however, the Confederates were defeated at Dungan's Hill, Cashel, and Knocknanuss, forcing them to agree to be placed under Royalist command; this, in turn, led to internal divisions which hampered their ability to resist a Parliamentarian invasion in 1649. The ensuing Cromwellian conquest of Ireland devastated the island, with Ireland losing 40% of its prewar population to war, disease, and famine. By 1652, most of the Confederate leaders had surrendered to Oliver Cromwell's Parliamentarian armies,and the prewar Irish Catholic landowning class was all but destroyed. Most senior Confederates went into exile in France, while the remnants of their armies were permitted to enter the service of France and Spain.
The Irish Confederates of the 1640s were a complex and multifaceted movement, with both conservative/Royalist and non-Royalist factions. The majority of the Irish Confederates were conservative and Royalist in their orientation; they were Catholic landowners and nobility who sought to defend the rights and privileges of the Catholic landed class in Ireland against the growing power of the Protestant English Parliament and the Puritan settlers. They supported the Royalist cause during the English Civil War, as they saw King Charles I as a bulwark against the spread of Protestant Puritanism.
However, there were also significant non-Royalist Irish rebel factions that emerged during this period. The Gaelic Irish lords and chieftains, such as the O'Neills and O'Donnells in Ulster, resisted both the English crown and the Royalist Confederates as they sought to maintain their traditional political and landholding power. The more radical Catholic Confederates, led by figures like Owen Roe O'Neill, were less concerned with defending the privileges of the landed gentry and more focused on wresting political and religious concessions from the English. They were willing to ally with the English Parliament against the Royalists at times. The urban, merchant, and professional Catholic classes in Ireland, particularly in cities like Dublin and Waterford, were less tied to the landed aristocracy and more sympathetic to Parliamentary republicanism.