The Irish military diaspora refers to the many people of either Irish birth or extraction (see Irish diaspora) who have served in overseas military forces, regardless of rank, duration of service, or success.
Many overseas military units were primarily made up of Irishmen (or members of the Irish military diaspora) and had the word 'Irish', an Irish place name or an Irish person in the unit's name. 'Irish' named military units took part in numerous conflicts throughout world history.[1][2][3] The first military unit of this kind was in the Spanish Netherlands during the Eighty Years' War between Spain and the Dutch. A notable example is that of Owen Roe O'Neill.