The name Irish Wolfhound is quite a recent one but the hound itself goes back far into the mists of time. It is mentioned, as cu (variously translated as hound, Irish hound, war dog, wolf dog, etc) in Irish laws, which predate Christianity, and in Irish literature which dates from the 5th century or, in the case of the Sagas, deom the old Irish period - AD600-900.
Only kings and the nobility were allowed to own the great Irish hound, the numbers permitted depending on position. For example, the Filid (the professional class of composers of sagas and other tales, who were of the lesser nobility) were entitled to two hounds. There were plenty of kings and nobles, as ancient Ireland was divided into fifths, each with a king, and each fifth comprised numerous kingdoms (there were 150 kingdoms in Ireland) each of which had a lesser kind subject to the kings of the fifths.
The wolfhound was originally a war dog, used to drag men out of chariots or off horseback, but was also used as a hunting hound and as a guard. There are numerous reference in Irish mythology to its prowess in all these fields. It was used to hunt the Irish elk and the wolf and was used singly or in pairs rather than in a pack, hence the need for great size. When the last of the wolves in Ireland was killed (the elk had become extinct long before), the breed dwindled and almost died out.
The process was not helped by the demand for this magnificent hound around the world. It was given as a gift to kings and princess, but this was eventually stopped by Oliver Cromwell who brought out a law banning its export. In later years, Environmental conditions like the great Irish potato famine and mass migration from Ireland, made the breed almost extinct.
In the middle of the Nineteenth century, Capt. George Augustus Graham undertook, with a small group of dedicated men, the resuscitation of the breed, which he did by collecting what he considered to be the last specimens of the breed. It was Capt. Graham who founded the Irish Wolfhound Club in 1855, and a later doyenne of the breed, Mrs. Florence Nagle, who founded the Irish Wolfhound Society in Great Britain in 1981.