The Anglo-Norman invasion of Ireland took place during the late 12th century, when Anglo-Normans gradually conquered and acquired large swathes of land from the Irish, over which the kings of England then claimed sovereignty, all allegedly sanctioned by the papal bull Laudabiliter. At the time, Gaelic Ireland was made up of several kingdoms, with a High King claiming lordship over most of the other kings. The Anglo-Norman invasion was a watershed in Ireland's history, marking the beginning of more than 800 years of direct English and, later, British, conquest and colonialism in Ireland.

The Anglo-Normans were the medieval ruling class in England following the Norman Conquest, and were primarily a combination of Normans, Frenchmen, Flemings, and Bretons who intermarried with the indigenous Anglo-Saxons and Celtic Britons. A small number of Normans had earlier befriended future Anglo-Saxon king of England, Edward the Confessor, during his exile in his mother's homeland of Normandy in northern France. When he returned to England, some of them went with him; as such, there were Normans already settled in England prior to the conquest. Edward's successor, Harold Godwinson, was defeated by Duke William the Conqueror of Normandy at the Battle of Hastings, leading to William's accession to the English throne.