The Battle of Knockdoe took place on 19 August 1504 at Knockdoe, in the Parish of Lackagh (Irish Leacach), County Galway, between two Anglo-Irish lordsGerald FitzGerald, Earl of Kildare, the Lord Deputy of Ireland, and Ulick Fionn Burke, 6th Clanricarde (d.1509)along with their respective Irish allies. The cause was a dispute between Maelsechlainn mac Tadhg Cellaigh (Mod. Irish Maoilseachlainn mac Thaidhg U Cheallaigh)(O'Kelly), King of Ui Maine Mod. Irish U Mhine) and Clanricarde.

The major contemporary sources for this battle are the Gaelic Irish annals and a sixteenth-century manuscript written in the Pale known as "the Book of Howth".

From the 12th century onwards, a group of Normans invaded and settled in Gaelic Ireland. These settlers later became known as Norman Irish or Hiberno-Normans. They originated mainly among Cambro-Norman families in Wales and Anglo-Normans from England, who were loyal to the Kingdom of England, and the English state supported their claims to territory in the various realms then comprising Ireland. During the High Middle Ages and Late Middle Ages the Hiberno-Normans constituted a feudal aristocracy and merchant oligarchy, known as the Lordship of Ireland. In Ireland, the Normans were also closely associated with the Gregorian Reform of the Catholic Church in Ireland. Over time the descendants of the 12th-century Norman settlers spread throughout Ireland and around the world, as part of the Irish diaspora; they ceased, in most cases, to identify as Norman, Cambro-Norman or Anglo-Norman.

The dominance of the Norman Irish declined during the 16th century, after a new English Protestant elite settled in Ireland during the Tudor period. Some of the Norman Irish—often known as The Old English—had become Gaelicised by merging culturally and intermarrying with the Gaels, under the denominator of "Irish Catholic". Conversely, some Hiberno-Normans assimilated into the new English Protestant elite, as the Anglo-Irish.

Some of the most prominent Norman families were the FitzMaurices, FitzGeralds, Burkes, Butlers, Fitzsimmons and Wall family. One of the most common Irish surnames, Walsh, derives from the Normans based in Wales who arrived in Ireland as part of this group.