Debateably seen as the oldest form of whiskey, Irish Whiskey is fairly straightforward in its production requirements. Being a whiskey, it must be distilled from grains, and typically they use barley.  It must be made in Ireland, it must be distilled at less than 94.8% abv (alcohol by volume), it must be aged at least three years in wooden barrels, and if it is a blend of two or more distillates, then it must be labeled "Blended".