This surname is practically the same in both its Irish and Anglicized forms. In Irish it is spelled "O Flannagain," which is probably derived from the adjective flann meaning reddish or ruddy. It belongs to Connacht both by origin and location (i.e. present distribution of population). Flanagan (and O'Flanagan, for this is one of those names with which the prefix is frequently retained) is sixty-ninth on the list of the most common surnames in Ireland. Spelling variations of the name include: Flanagan, Flanaghan, Flangan, Flanigan, Flannagan, Flannigan, Flanningan, Flanikin, Flanakin, Flanagin, Flanigin, Flenniken, Flannacan, Flannacain, and any of these prefixed with an O'. Names derived from FLANN, are Flanagan, Flanagin, Flannagan, Flanaghan, Flanigan, Flinn, Flynn, Glenn, Glynn, Linn, Lynn, Macklin, Maglin, Maglon, McGloin, MacFlancha, Clanchy, Clancie, Clancy, MacClanchy, Clinch and Clanchy.
Flanagan, first recorded in 9th century Ireland, was the surname of five distinct families located in diverse parts of the country. The principal Flanagan sept, originally established in County Roscommon, remains numerous there today as well as the western seaboard counties Mayo, Galway and Clare. A branch of the Sil Murray, they descend from Muireadhach Muilleathan, King of Connacht [d. 701]. Flanagan, from whom they derived their surname, was of the same lineage as the royal O'Connors, his heirs holding the hereditary post of Steward to the Kings of Connacht and Chiefs of Clan Cathail, a considerable district which embraced several parishes in the area lying between Mantua and Elphin. Their Chief was seated in Frenchpark in Roscommon. Another leading sept, founded in Waterford were Chiefs of Uachtartire in Upperthird barony in the northwest of the county. For over three hundred years, they were the predominant family in the region until unseated by the Anglo-Norman Powers. Ulster Flanagans, Chiefs of Tuath-ratha, were of the Oirghialla Clan; their ancestors were the celebrated Three Collas, 4th century Chiefs of the province. These Flanagans controlled a vast territory in Magheraboy barony, in northwestern Fermanagh. Of the two Leinster septs, the Flanagans of Ely O'Carroll were the more prominent. Together with the O'Carrolls, they stemmed from the Lord of Ely who fought at Clontarf in 1014. Until the Anglo-Norman invasion in the year 1171, they were Chiefs of Cinel Arga, a district co-extensive with the present day barony of Ballybrit, County Offaly. In early times the Flanagans of County Westmeath were one of the most important in the province of Leinster, being Lords of Comair and sometimes of all Teffia.
Flanagans have migrated to every corner of the globe. In the internet age, an international family association has been formed called ClanFlanagan. Affiliated with the Clans of Ireland, the goals of ClanFlanagan are to provide a venue for sharing historical and genealogical information as well as social interaction between Flanagans of all lines.
Those who have websites which include details of Flanagan Genealogy are encouraged to add their Flanagan websites to this list: