The Cromwellian conquest of Ireland (1649–1653) was the re-conquest of Ireland by the Commonwealth of England, initially led by Oliver Cromwell. It forms part of the 1641-to-1652 Irish Confederate Wars, and wider 1639-to-1653 Wars of the Three Kingdoms. Modern estimates suggest that during this period, Ireland experienced a demographic loss totalling around 15 to 20% of the pre-1641 population, due to fighting, famine and bubonic plague.
The Irish Rebellion of 1641 brought much of Ireland under the control of the Irish Catholic Confederation, who engaged in a multi-sided war with Royalists, Parliamentarians, Scots Covenanters, and local Presbyterian militia. Following the execution of Charles I in January 1649, the Confederates allied with their former Royalist opponents against the newly established Commonwealth of England. Cromwell landed near Dublin in August 1649 with an expeditionary force, and by the end of 1650 the Confederacy had been defeated, although sporadic guerrilla warfare continued until 1653.