To all those with Gallagher, or any of its many variations, in their family tree, join us in celebrating our heritage. Clan Gallagher / Uí Ghallchobhair is an Irish family whose roots stretch back to ancient times. Clan Gallagher reunited in 2005 after 400 years of separation. Seán Ó Gallachóir, President of the Clan Gallagher Organization, 2005; and in 2007, in Letterkenny, Ireland, under the leadership and with the invaluable work of Eve Gallagher and  Adrian Gallagher, the Guinness World Record for the largest gathering of a single surname in history was broken. 1,488 Gallaghers from all over the world attended.