Gaelic Ireland was the Gaelic political and social order, and associated culture, that existed in Ireland from the late prehistoric era until the 17th century. It comprised the whole island before Anglo-Normans conquered parts of Ireland in the 1170s. Thereafter, it comprised that part of the country not under foreign dominion at a given time. For most of its history, Gaelic Ireland was a "patchwork" hierarchy of territories ruled by a hierarchy of kings or chiefs, who were chosen or elected through tanistry. Warfare between these territories was common. Traditionally, a powerful ruler was acknowledged as High King of Ireland. Society was made up of clans and, like the rest of Europe, was structured hierarchically according to class. Throughout this period, the economy was mainly pastoral and money was generally not used. A Gaelic Irish style of dress, music, dance, sport and art can be identified, with Irish art later merging with Anglo-Saxon styles to create Insular art.

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.