Saint Patrick's Saltire or Saint Patrick's Cross is a red saltire (X-shaped cross) on a white field, used to represent the island of Ireland or Saint Patrick, the patron saint of Ireland. In heraldic language, it may be blazoned Argent, a saltire gules. Saint Patrick's Flag is a flag composed of Saint Patrick's Saltire.
There is no universally accepted flag for the island of Ireland. Saint Patrick's Saltire dates only from the late eighteenth century, although there is some evidence of a similar saltire's earlier use as a symbol of Ireland, possibly deriving from the coat of arms of the powerful Geraldine or FitzGerald dynasty. Its relatively recent origins have led to it being rejected by some Irish nationalists as a "British invention",although it predates the use of the Irish national flag by at least 150 years.
St. Patrick's Saltire was first used in the regalia of the Order of Saint Patrick, a British chivalric order established in 1783 by George III, and later in the arms and flags of a number of institutions. After the 1800 Act of Union joined the Kingdom of Ireland with the Kingdom of Great Britain, the saltire was added to the British flag to form the Union Flag still used by the United Kingdom. The saltire has occasionally served unofficially to represent Northern Ireland and been considered less contentious than other flags flown there.