In Co. Fermanagh, where the name is also numerous, the family are thought to be part of the original inhabitants of the area, the Fir Manach, from whom the county gets its name. Their base was in the district of Lurg. From here the name has now also scattered in the adjoining counties of Monaghan and Derry.
There were 140 births of the name in Ireland in 1890, concentrated in Galway, Mayo and Fermanagh. It was ranked 150th in 1890 and 151st in 1996.
James Henry Monaghan (1804-1878), from Galway, became Lord Chief Justice of Ireland and was responsible for the prosecutions of the Young Irelanders and the Fenians.
Philip Monahan (1894-1983) fought in the War of Independence and afterwards became an influential civil servant. He was appointed City Manager of Cork for life at the age of 35.
Rinty Monaghan (1920-1984), the Belfast boxer, became world flyweight champion in 1947 and retired undefeated in 1949, suffering from tuberculosis.