Flag of Ulster

The Flag of Ulster is a historic banner used to represent Ulster, one of the four provinces of Ireland. The Red Hand of Ulster is a symbol that is either derived from the O'Neill dynasty, then the most prominent Irish clan in Ulster, or the Dextra Dei of early Christian iconography. The gold background featuring a red cross comes from the coat of arms of the Burkes, a Hiberno-Norman noble family.

The arms of the historic province of Ulster is a composite achievement, combining the heraldic symbols of two of that province's best known families, namely the cross of de Burgh and the red hand motif adopted by the O Neill (Ua Néill, later Ó Néill) Kings of Ailech and Tír Eoghan. The celebrated 'Red Hand' badge of O'Neill was probably grounded on a theme in Gaelic mythology. It may have originally symbolized the pre-Christian Celtic sun-god Nuadu ('he who dwells in the clouds'), also known as Argatlámh ('silver hand') and his alias Bolg had a son named Lámhdearg ('red hand') or Labraid. Alternatively it may be based on the Dextra Dei, which had long been employed as a Christian symbol in early Christian iconography. In early Christian iconography God the Father was frequently represented by the open right hand, sometimes within a halo or nimbus. An example of this motif can be seen on the ring of the 10th century High Cross of Muiredach at Monasterboice, County Louth. An early heraldic use in Ireland of the open right hand can be seen in the seal of Aodh Ó Néill, King of the Irish of Ulster, 1344-1364.

Active participants in the First Crusade (1096–99), which ushered in the heraldic era, among them members of the de Burgo family of Tonsburg in Normandy, fashioned crosses in fabric on their apparel before leaving for the Holy Land. One Walter de Burghe is recorded in a thirteenth-century roll of arms (Walford Roll) as bearing a red cross on his shield.

When Walter de Burgh, Lord of Connacht, became Earl of Ulster in 1243 the de Burgo cross became inseparably linked with the Hiberno-Norman Earldom of Ulster, which spanned over a third of the province. The seal of his son Richard, for example, appended to a deed dated 1282, shows the heraldic cross in triplicate together with what may well be a portrait head of the Earl himself. At some point the Red Hand motif was appended to the de Burgo cross, the result eventually coming to represent the entire province.

...
Wikipedia