Murphy is by far the most frequently found surname of Irish origin with well over 50,000 bearers of the name in Ireland alone. This name is derived from two distinct Gaelic septs. The first of these was O'Murchadha and the second was MacMurchadha. The name is taken from words that translate as 'sea warrior'. Murphy is only very occasionally rendered as O'Murphy or MacMurphy. Other variants of this widespread name include Murphey, Murfee, Morphy and O'Morchoe.

There were septs in Counties Tyrone and Sligo but by far the most important sept was located in Leinster Province, and especially in County Wexford. A sept is similar to a clan, and refers to a group of people who inhabited the same locality and who shared the same name. In modern times the name has become even more associated with the Munster Counties of Cork and Kerry than its originating County of Wexford. The Munster sept of Murphy is a branch of the Kinsellas who also hail from the Wexford Murphys. The northern Murphys are today most often found in Counties Tyrone and Armagh.

It is impossible to discuss the origin of the Murphys without also mentioning the MacMurroughs. The most famous (or infamous) was Dermot MacMurrough who was partly responsible for the Strongbow Anglo-Norman invasion of 1170. Dermots grandfather was Murchadha whose original sept split into three branches giving the MacMurroughs, the Kinsellas and the Kavanaghs. His brothers are the origin of the O'Morchoes and MacDavie Mores, who changed their original names to Murphy and Davis respectively. All of these families are most associated with County Wexford.

The Wexford Murphys held territory in the barony of Ballaghkeen, formerly known as Hy Felimy from one of the sons of Eanna Cinnseallaigh, the fourth century ruler of Leinster. Their chief seats were located at Morriscastle, Toberlamina, Oulart and Oularteigh. The last chief to be elected by the ancient Gaelic method of tanistry was Murtagh who in the year 1461 adopted English law entitling him to leave his lands and property to his descendants. His ancestor Donal Mor O'Morchoe was overthrown at the end of the sixteenth century and his lands confiscated. The Murphys of Oularteigh retained their lands and remained there up to modern times. A Tipperary branch of the Murphys had their land confiscated by Cromwell.

Famous Murphys throughout history include Domhnall Dall Ua Murchadha who was 'chief sage of Leinster' in the year 1127. Two Catholic priests were killed during the Wolfe Tone 1798 rebellion, they being Rev John Murphy (1753-1798) and Rev Michael Murphy (1767-1798). Sean O'Murchadha (1700-1770) was the last chief of the Blarney bards in Cork. Marie Louise O'Murphy (1737-1814) was a daughter of an Irish soldier at Rouen and became mistress to Louis XV. Patrick Murphy (1834-1862) was remarkable for his height of eight feet one inch. The Ladys Well brewery that produces Murphys Stout was founded in 1856 by James Murphy. William Martin Murphy (1844-1921) was the leader of the employers against the strikers in Dublin in 1913. Michael Murphy (cir 1837-1893 in County Tipperary) was an Irish recipient of the Victoria Cross, the highest British award for gallantry. Audie Murphy (1924-1971) was the recipient of America's highest award known as the Medal of Honor and remains one of the most decorated soldiers in US history.

Over the centuries the name Murphy has been spread by emigration to England, Australia, Canada, America and beyond with the influence of bearers of the name being found in every sphere of life.