The national flag is a tricolour of green, white and orange. The three colours are of equal size, vertically disposed, and the green is displayed next to the staff. Some say that the flag is gold as opposed to orange, from the gold harp on the original Green Flag.

This confusion arose in the 1916-22 period when the tricolour (the current national flag and ensign), which had previously been quite a marginal and little-known flag, was supplanting the Green Flag (the current jack) as the principal national emblem. Green and gold, the colours of the Green Flag, were regarded as the national colours throughout the nineteenth century and some of the home-made tricolours from the 1916-22 period were in fact green, white and gold. There are also some songs from that period which refer to 'green, white and gold' flags and this helped to keep the concept alive, but the symbolism of the green, white and orange dates from 1848.

The flag was first introduced by Thomas Francis Meagher during the revolutionary year of 1848 as an emblem of the Young Ireland movement, and it was often seen displayed at meetings alongside the French tricolour.

The green represents the older Gaelic and Anglo-Norman element in the population, while the orange represents the Protestant planter stock, supporters of William of Orange. The meaning of the white was well expressed by Meagher when he introduced the flag. 'The white in the centre', he said, 'signifies a lasting truce between the 'Orange' and the 'Green' and I trust that beneath its folds the hands of the Irish Protestant and the Irish Catholic may be clasped in heroic brotherhood.'

This flag didn't come into general usage until the war of independance (1919-1921). Prior to this, the green flag with gold harp was the main symbol of nationalism. t was not until the 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, but only at the creation of the first "Dail" ( House of Representatives /Commons) did the current Tricolour become widely used and its use as a national flag is firmly established in the Constitution: Article 7 of "Bunreacht na hEireann" ( constitution of Ireland) states "The National Flag is the Tricolour of Green, White and Orange."