The project is open to all O'Callaghan, Callaghan & Callahan, Keelaghan, Kelaghans, (and variants) whose families originated in Ireland, especially Counties Cork, Mayo, Tipperary and Clare.  It would be great to document all Callahans whether you live in Ireland, England, Canada, The United States, Spain, Australia and New Zealand (or wherever the wind  took you!)  Please feel free to join us if you have Family Finder results and have a documented Callahan in your background even though we cannot as of yet display you on the Public web page. 

The surname means descendant of Ceallachán who was the Eóganachta King of Munster from AD 935 until 954. The personal name Cellach means ‘bright-headed’.  The Callaghan lands were traditionally west of Mallow, Cork along both sides of the Blackwater river valley, comprising the parishes of Kilshannig and Clonmeen.  The Callaghan’s were dispossessed of their ancestral home of approximately 50,000.00 acres during the Cromwellian Plantation and settled in East Clare. 

Please see historical map circa. 1209 which shows the O'Callaghan Clan in Munster along the Blackwater River at http://www.logainm.ie/eolas/Data/TCD/tcd-1209-1.jpg

Ó Ceileacháin in Irish, is to be found in the counties Armagh, Louth, Meath and Monaghan. It has been anglicized as Callaghan, Kelaghan, Keelaghan, Kealahan and other variants. In County Meath, where it is widespread but has been found mainly in the parishes of Kells, Trim and Athboy, it is mainly anglicized as Callahan, Callaghan or O'Callaghan (with local spelling variants). In County Westmeath it is still found in the form Kelaghan. In County Monaghan it is often found as Keelan. Members of the Ó Ceileacháin family were mentioned in the Annals of the Four Masters as being lords of Uí Breasail, a district on the southern shore of Lough Neagh, and priors of Armagh in the 11th century. 

There is also a Mayo family of this name, a branch of the Ui Fiachach, who were anciently the lords of Erris.   See Patrick Woulfe, Irish Names and Surnames (1923).