The national flag of Ireland (Irish: bratach na hÉireann) – frequently referred to as the Irish tricolour (trídhathach na hÉireann) – is a vertical tricolour of green (at the hoist), white, and orange
Formally adopted in 1922 (Constitutional status; 1937) the proportions of the flag are 1:2 (that is to say, flown horizontally, the flag is half as high as it is wide).
The Irish government has described the symbolism behind each colour as being that “green represents the older Gaelic tradition while the orange represents the supporters of William of Orange. The white in the centre signifies a lasting truce between the ‘Orange’ and the ‘Green’.” 
Presented as a gift in 1848 to Thomas Francis Meagher from a small group of French women sympathetic to the Irish cause, it was not until the Easter Rising of 1916, when it was raised above the General Post Office in Dublin, that the tricolour came to be regarded as the national flag. Meagher was the son of Newfoundland-born mayor of Waterford, Thomas Meagher Jr. However, there are two theories on his inspiration for the flag: the similarly-coloured Newfoundland Tricolour credited in legend as having been created in 1843, though this seems unlikely given the actual known history surrounding the Newfoundland Tricolour; and the French Tricolour.
The flag was adopted in 1916 by the Easter Rising rebels and subsequently by the Irish Republic during the Irish War of Independence (1919–1921). Its use was continued by the Irish Free State (1922–1937) and it was later given constitutional status under the 1937 Constitution of Ireland. The tricolour is used by nationalists on both sides of the border as the national flag of the whole island of Ireland since 1916. Thus it is flown by many nationalists in Northern Ireland as well as by the Gaelic Athletic Association.