Ireland is an island nation located off of Great Britain.
In 1649, The Doctor, Ace and Hex visited Ireland during Oliver Cromwell's siege of Drogheda. (BFA: The Settling)
'Gallifrey' is often mistakenly located in Ireland.
Home of Sean (DW: The Underwater Menace), Sean Flannigan (DW: The Wheel in Space), McDermott (DW: Terror of the Autons), Casey (DW: Talons of Weng Chiang) and possibly Luke Rattigan (DW: The Sontaran Stratagem/The Poison Sky). Chip (DW: New Earth) and Thomas Kincade Brannigan (DW: Gridlock) both have Irish accents, but neither character can ever have been to Ireland.