History of the Clan

The surname O’Sullivan or in Irish Ó Súilleabháin traces its origin from Míl Espáine or Milisius, King of the Milesians (or Celts), King of Spain through the line of his son, Heber, first absolute King of Ireland 504 BC. The surname O’Sullivan is derived from the words Súil (eye) and abháin, (one) and in its Irish form Ó Súillabháin means descendant of the one eyed or descendant of the hawk-eyed. The O’Sullivans were descendants of Eoghan (Owen) Mór, the father of the famous Olioll Olum, celebrated King of Munster in the third Century. Olioll Olum had three sons, Eoghan, Cormac Cais and Cian, and by his will he commanded that the kingdom should be ruled alternately by one of the descendants of Eoghan and Cormac Cais. From Eoghan, the eldest son of Olioll Olum, descended the Eoganachts or Eugenians, who were styled Kings of Cashel. The Eoghanachts possessed Desmond or south Munster, the present counties of Cork and Kerry; they also held most of the present county of Tipperary. The O’Sullivans were one of the principal families of the race of Eogan or Eoghanacht (i.e. descendants of Eoghan) of Munster.

There were three principal branches of the
O’Sullivan Clan:-

1. O’Sullivan Beara

This branch of the family had the ancient territory of Beara, now the baronies of Beare and Bantry in the county of Cork, and were called O’Sullivan Beara and styled princes of Beara.

2. O’Sullivan Mór

This branch of the family were lords of Dunkerron, they possessed the barony of Dunkerron near the river Kenmare and their chief seat was the castle of Dunkerron.

3. O’Sullivan of Croc Raffan

This branch of the O’Sullivans were chiefs of Knockgraffan in Tipperary and the territory they
possessed in Tipperary was situated in the
barony of Middlethird, between Cashel and Cahir.

The name O’Sullivan and its variant forms are the third most numerous surname in Ireland. There are an estimated 41,500 bearers of the name resident in the island at the present time. However, we must not forget that there are possibly ten times that total of O’Sullivans living outside the shores of Ireland, in the two Americas, Canada, Australia, New Zealand, England, Europe, the African Continent and to a lesser extent Asia and the rest of the world. There is an O’Sullivan family in every county in Ireland, but the main branch of the family is associated with the province of Munster.

The O’Sullivan’s of Munster

The O’Sullivan’s of Munster are descended from Olioll Olum, King of Munster, through his descendants the Eoganachts to Aodh Dubh were the first princes of Eoghanacht Mór, Cnoc Graffan, in the Barony of Middlethird and their lands included Clonmel, Cahir, Carrick-on-Suir, and Cashel.
O’Heerins verse recalls their former glory:  
O’Sullivan who delights not in violence
Rules over the extensive Eoghanacht of Munster
About Knockgraffan he obtained his lands
After the victory of conflicts and battles.

The name of the O’Sullivans territory in Tipperary is still retained in the parish of Knockgraffan, where the O’Sullivans had their principle seat, and in which is an ancient mound or rath near the river Suir, which was a residence of the Kings of Munster. 

 In 1193 the Normans forced the O’Sullivans of Knockgraffon to exchange their fertile lands in Tipperary for the mountains in Cork and Kerry. The Normans later built a castle on the symbolic rath of Knockgraffan depriving the O’Sullivans of their historic seat of power. The O’Sullivans driven out of their territories in Tipperary moved south and by conquest took possession of the greater part of the Baronies of Glanerought, all Dunkerron and a considerable portion of Iveragh in Kerry. 

 From their first coming into Cork and Kerry the clan divided into two great branches – O’Sullivan Mór and O’Sullivan Beare. The O’Sullivan Beare took the lands south of the Kenmare River, which consisted of the Baronies of Beare, Bantry and Glanerought. The seat of the Chief of the O’Sullivan Beare branch was at Dunboy and he also held the Castles at Bantry and Carriganass.   The territory of the O’Sullivan Mór was more extensive. It was bounded by the shore of Kenmare Bay from Caherdaniel to Kenmare in the east, in the north by a line drawn from Kenmare to Killorglin, in the west by the shoreline of Dingle Bay, in the south by the coastline from Derrynane Bay to Valentia Island. The principal castle of the Chief O’Sullivan Mór at Dunkerron was two miles west of Kenmare town. Dunloe Castle, six miles from Killarney, was also built by O’Sullivan Mór in the thirtieth century and was used to guard the only pass (Gap of Dunloe) which gave access from north Kerry to his country.

Having spent some time resting with O’Rourke he went to Ulster and accompanied Hugh O’Neill to London to ask pardon and restoration of his lands from James I. Like O’Neill, O’Sullivan was also refused a formal pardon and on returning to Ireland he made preparations to sail for Spain with his wife and family.  He sailed for Spain in 1604 and was received with open arms by King Philip III of Spain, who made him a knight of St James and Count of Berehaven and gave him a monthly income. He lived for fourteen years in exile in Spain under the patronage of the King, until he was struck down by a servant’s knife in July 1618 in Madrid. His son Donal died fighting at the siege of Belgrade in the service of France. Donal’s brother Dermot, who had been on the march with him to Leitrim, also travelled to Spain with him. This Dermot O’Sullivan brought his wife, son Donald and his two daughters, Helen and Nora, to Spain with him, where he lived to the age of 100 years and is buried in the Franciscan Church in Corunna.
Philip O’Sullivan Beare commonly known as Don Philip, son of Dermot O’Sullivan Beare and nephew of Donal O’Sullivan Beare was born 1590 at his father’s castle in Dursey Island. He was sent to Spain 1602 as hostage to King Philip III in return for agreed aid to the O’Sullivans. Having received his education at Compostellan he joined the Spanish Navy and served his time aboard the Spanish ships of war. 

 In 1619 he was aboard the squadron requested to escort the fleet carrying treasure to Cape St Vincent. His written accounts of their action against Barbery Pirates make interesting reading, and his literary talents were beginning to show. He soon devoted himself to writing and his important work Historia Catholicae IberniaeCompendum produced in Lisbon in 1621 is the story of the Elizabethan Wars written as he heard them from his uncles, his father and others of their time – details of Donal’s epic march, the battles, the hunger, and heroism is all there, it also contains details of the pilgrimage to St Patricks Purgatory, the English in Ireland from the Anglo Norman invasion to 1588, and a history of O’Neill and O’Donnell’s wars.  

Patricanna Deces
 and the Life of St Patrick and his numerous other books were all written in Latin. He remained, although exiled, deeply devoted to Ireland. The biggest cross he had to bear in exile was the death of his near relatives in a short space of time. His sister Helen was drowned while on a voyage home to Ireland, his brother Daniel was killed fighting the Turks and his parents died within a couple of years of each other. His death in 1660 was recorded by Father Peter Talbot, later Catholic Archbishop of Dublin, as follows: 'The Earl of Berehaven is dead and left only one daughter of twelve years to inherit his titles in Ireland and his goods, here which amount to 100,000 crowns.’