The Cromwellian conquest of Ireland or Cromwellian war in Ireland (1649–1653) was the re-conquest of Ireland by the forces of the English Parliament, led by Oliver Cromwell, during the Wars of the Three Kingdoms. Cromwell invaded Ireland with the New Model Army on behalf of England's Rump Parliament in August 1649.

By May 1652, Cromwell's Parliamentarian army had defeated the Confederate and Royalist coalition in Ireland and occupied the country, ending the Irish Confederate Wars (or Eleven Years' War). However, guerrilla warfare continued for a further year. Cromwell passed a series of Penal Laws against Roman Catholics (the vast majority of the population) and confiscated large amounts of their land. As punishment for the rebellion of 1641, almost all lands owned by Irish Catholics were confiscated and given to British settlers. The remaining Catholic landowners were transplanted to Connacht. The Act of Settlement 1652 formalised the change in land ownership. Catholics were barred from the Irish Parliament altogether, forbidden to live in towns and from marrying Protestants.