O'Sullivan Clan History

This article considers the history of the O'Sullivan clan back to the fist Irish nobleman to take on the name, and further back to his ancestors. The article is based on recent research that considers both documentary and DNA evidence, plus content from the international O'Sullivan Clan website.


The O’Sullivan / Sullivan Clan and Family History


In this history the O’Sullivan and Sullivan names are treated as one. The “O” prefix denotes a descendant of, eg grandson of. Dropping the “O” leaves the anglicised version of the name. Much of the anglicisation took place when English administrators or clerks simply used the anglicised version in their daily dealings. There is little evidence to suggest people with the “O” prefix were forced for various reasons to drop the “O” by their English masters.

The first Irishman to take the Sullivan name lived over a thousand years ago, so in considering genealogy and family history we need consider some relevant customs and conditions that prevailed during this period.

From ancient times Irish society was organised around traditional kinship groups or clans. This was a large group of related people supposedly descended from one progenitor through male forebears. Although these groups were primarily based on blood kinship, they also included those who were fostered into the group and those who were accepted into it for other reasons. These clans traced their origins to larger pre-surname population groupings or clans such as Eoghanachta in Munster. Within these larger groupings there tended to be one sept (division) who through war and politics became more powerful than others for a period of time and the leaders of some were accorded the status of royalty in Gaelic Ireland.

The larger or more important clans were led by a Taoiseach or Chief who had the status of royalty and the smaller and more dependent clans were led by Chieftains. Under Brehon Law (see below) the leaders of Irish clans were appointed by their kinsmen as custodians of the clan and were responsible for maintaining and protecting their clan and its property. The clan system formed the basis of society up to the 17th century.

  • Primogeniture and Tanistry

Primogeniture is the right by law or custom of the legitimate firstborn son to inherit his parents’ estate and titles if any, in preference to daughters, older illegitimate sons, younger sons and collateral family. So genealogies tend to follow the line of primogeniture descent, especially the inheritance of royal titles.

Tanistry. In Gaelic Ireland succession to clan leadership was through a process called Tanistry. When a man became chieftain or king, a relative was elected at the same time to be his deputy or 'tanist'. When the chieftain or king died, his tanist would automatically succeed him. The tanist had to be male, to share the same great-grandfather as his predecessor and he was elected by freemen who also shared the same great-grandfather. Also, the Tanist held office for life and was required by custom to be of full age, in possession of all his faculties and without any remarkable blemish of mind or body. Tanistry meant that the leadership usually went to whichever relative was deemed to be the most fitting . Most usually a former leader’s son became tanist, not because the system of primogeniture was in any way recognized, but on the principle that the dignity of leadership should descend to the eldest and most worthy of the same male-line blood of the clan.

This system often led to rotation among the most prominent branches of the clan or the reigning house, particularly in the Middle ages. The average lifespan was then usually shorter than required for one's children to grow into mature adults.] Tanistry, though not necessarily intended to be so, was perceived to create balance between branches of family. However this meant that the group could become highly exclusive, keeping the leadership within the dynasty. Many in the wider clan might be reduced to gentry or peasant status, even though they might share the surname.

The downside of the large group of eligibles was that increases in suitable candidates in each generation might lead to internecine dynastic civil war. It was a frequent source of strife both in families and between the clans, but it was conversely quasi-democratic. War within or between clans usually involved elimination of one protagonist or their exclusion from the clan territory

Tanistry as the system of succession left the headship open to the ambitious. Occasionally ambitious and capable leaders who were not elected Tanist might choose to break away from the clan and form a new sept, or offshoot of the original clan. This clan could even become more powerful over time and eventually overshadow the original clan.

In Ireland, Tanistry continued among the dominant dynasties, as well as lesser lords and chieftains, until the mid-16th century when it was replaced by English common law Tanistry was abolished by a legal decision during the reign of Jamess I of England and Ireland.

  • Brehon Law was the name given to the ancientGaelic-Irish law that existed prior to the coming of Christianity in the 5th century, was gradually modified by the Roman law that came with the Christians, was partially eclipsed by the Norman invasion of 1169, then enjoyed a resurgence between the 13th and 17th centuries. It was then outlawed as “barbarous” by the English as it had been what had kept the English from implanting its feudal system and completing its conquest of Ireland.

Primogeniture was part of Brehon Law, although property was inherited by sons on a partition basis. Under Brehon Law women had a more rights and higher marital status than under the patriarchal Roman law, being treated more as partners than property. Divorce could be initiated by either party, and hence was more prevalent, with consecutive marriage a prominent feature of Irish society, especially among the aristocracy.

Polygyny – the marriage of a man to more than one woman at a time - was also recognized in pre-Norman Ireland. The Brehon laws recognised that variations could arise in the affections of men and women towards each other and they legislated for these rather than simply condemning them as illegal. Those who could afford more than one wife were legally entitled to do so, which of course was not in line with the Christian Church’s ideas on the matter. The acceptance of polygyny meant that the number of descendants of chieftains could rapidly reach major proportions over time. The Brehon Law humanely legislated for all children, irrespective of the circumstances of their conception, and their rights were recognised. The laws were not framed for the notion of a single lawful marriage, only the issue of which could be deemed legitimate. Basically, the notion of “illegitimacy” was foreign to the Brehon Law and children were not narrowly branded as under Norman law.

  • Genealogy Resources

Ireland has a rich literature that dates back to the 5th century. Much older traditional histories dating back to the first Irish settlers appear in the annals of Ireland written by monks in monasteries, based on ancient verbal histories. The annals of Clonmacnoise is the most prominent and comprehensive of these annals, written in the Irish Gaelic language, and covers a time period ending in 1408, suggesting the annals were written sometime after this date. There is archaeological, linguistic and DNA evidence supporting statements made in the Annals of Clonmacnoise. From the 5th century on the evidence is supported by other historical accounts..

The Gaelic Celts

There is abundant archaeological evidence that Ireland was inhabited in the Mesolithic period from circa 8000 BC. In the Neolithic period from 4000 BC to 2000 BC agriculture and animal husbandry was practiced in Ireland.In the Bronze Age from 1220 to 700 BC, bronze weapons, tools and household goods were being manufactured.

DNA evidence has established that the Celts were in Ireland in the Neolithic period. The evidence also suggests the Gaelic Celts came from Spain, and probably from an area on the northern Atlantic coast, populated by the Basque people who exhibit a Celtic culture.

Linguistic evidence considers that Insular Celtic (British Isles and Ireland) separated as a distinct branch of the Celtic language 4,500 years ago, placing the Celts in Ireland before 2500 BC.

According to the Annals of Clonmacnoise, Milesius born in 1046 BC was King of the Celts in Spain. His sons led a settlement party to Ireland where they subjugated and/or merged with the indigenous population and established their own dynasty.

Royal Origins

The ancestor of most interest in the kingly dynasty was King Finghin of Munster and Lord of Cashel who was born in 571 AD. At that time Ireland was subdivided into a number of main kingdoms, as shown on the adjoining map.

Finghin claimed direct descent from Milesius and was a member of the Eoganachta, a Gaelic Irish dynasty centred on Cashel in Tipperary which dominated southern Ireland from the 6/7th to the 10th centuries, and following that, in a restricted form, the Kingdom of Desmond and its offshoot Carbery to the late 16th century.

The rule of the Eóganachta in Munster is widely regarded as gentle and more sophisticated in comparison with the other provincial dynasties of Ireland. Not only was Munster the wealthiest of the provinces, but the Eóganachta were willing to concede other previously powerful kingdoms, whom they had politically marginalized, considerable status and freedom from tribute, based on their former status as rulers of the province.

The Eóganacht king Finghin ruled as King of Munster (died 618) and is the direct male line ancestor of the O'Sullivans. His son Seachnasagh (born 606) was too young to assume the throne and Finghin was therefore followed by his younger brother Failbe Flann as Eóganacht king of Munster, and he was the direct male line ancestor of the later MacCarthy kings. So Finghin’s death ended the direct line from Milesius.

Seachnasagh took the title of lord of Knockgraffon. This was an ancient castle on the river Suir near Cashel and not far from Clonmel.. The ancestors of King Finghin had occupied Knockgraffon until about 350 AD when they built Cashel Castle, which then became the traditional seat of the Kings of Munster.

Seachnasagh’s descendants were Fiachra na Gaircedh, Flann Noba, Dubhinracht, Morough, Moghtigern, Maolura and finally in 874 Eochaid, all lords of Knockgraffon. So Eochaid was an 8th generation direct descendant of King Finghin.

The Early O’Sullivans

Eochaid took the nickname Suilleabhainn, roughly translated as “dark eyed” or more likely “hawk eyed” or even “with raptor like eyes.” The anglicized name is Sullivan. Eochaid’s descendants became the O’Sullivan clan, who continued to reside at Knockgraffon castle.

Y chromosome DNA studies have shown links between the O’Sullivans and McCarthys dating back to the 7th century. Recent DNA studies of some Sullivans have found a common ancestor around 548 +/- 148 years.

Suilleabhainn became the head of one of three segments of Cenel Finghin, a subgroup of the Eogenachta Chaisil – effectively the descendants of Finghin. The other segments were the McCarthys and the Ui Donnchada, the latter being the senior line. Somewhere around 1000 to 1070 there was a civil war in Eogenachta Chaisil between these two other lines. The McCarthys took control of Emly and the western half of the kingdom, with the Ui Donnchada forced to the easy, with Cashel in dispute between both. It appears the O’Sullivans sided with the McCarthys against the senior line of Ui Donnchada who were subsequently wiped out. The subsequent tradition of the O’Sullivan chief as being the key person in the crowning of the McCarthy king by presenting him with the white hazel “rod of office” probably dates back to this time.

Lorcan, son of Eochaid, lord of Knockgraffon, was born about 914 AD and ruled as Chief of the senior Eoghanacht line. During his reign, a terrible famine struck Ireland in 963. Four years later the annalists reported a bumper crop of fruit. His son, Buadhach Atha-Cra, was born about 954 AD and also served as the lord of Knockgraffon.  Aodh, born about 994 AD, Cathal, born about 1034 AD, and Buadhach, born about 1074, all reigned as Chief of the clan and lord of Knockgraffon in their turn.

Aodh, lord of Knockgraffon, the O’Sullivan Mor, was only 19 years old when King Brian Boru defeated the Vikings at the Battle of Clontarf in Dublin. It is unknown whether or not any Eoghanacht troops participated in this victory. Great celebrations were held throughout Ireland with the news that the Vikings had been expelled. It would be nearly two centuries before another serious threat would appear on the shores of the “Island of Saints”, the Normans.

In the meantime, the violent politics of Munster kept the O’Sullivan clan quite occupied. Buadhach, which translates into Victor, was the first in the line to officially adopt the surname “O’Sullivan”. It was not a family name in this time, but rather a title identifying the chief of the clan. Buadhach would have been referred to as ‘the O’Sullivan Mor’, or “the Great O’Sullivan”.


MacCraith, son of Buadach, born about 1114 AD, was the last to die as lord of Knockgraffon. He was killed in 1176 while defending the king of Munster from his own son, Cormac Liathanach MacCarthy. MacCraith’s son, Donal Mor, born about 1134 AD, avenged his father’s death in the same year when he, and a group of other Eoaghanacht noblemen, killed Cormac and restored Dermot to the throne.

The O’Briens forced the McCarthys out of Cashel around 1100, although they probably remained around Emly as well as Cork. The McCarthys regained Cashel in 1118 and held it until 1138, at which time the McCarthy powerbase shifted to Lismore and Cork. They remained in this area until about the 1170s when the advancing Normans drove them into West Cork.

The O’Sullivans were allies of the McCarthys during this period. There is evidence that theO’Sullivans were still at Knockgraffon around 1130, and in the early 1200s other evidence suggests they were also around Lismore. It’s reasonable to conclude that they settled in the Lismore area under the McCarthys in the mid 1100s.

The Norman Invasion (1169-1270)

Ireland was the only society in Europe that had not been subjugated by Rome, decimated by the Dark Ages, and over run by barbarians. Throughout the first millennium AD, the Irish culture remained pure, Celtic, and distinctive. This insular immunity to the debacles of Europe came to a gradual and agonizing end with the arrival of the Normans.

The Normans originated from a Viking settlement in the west of France that had conquered England one hundred years before invading Ireland. Henry II was their French speaking king. In 1155, around about the time the O’Sullivans were shifting to Lismore Henry wrote a letter to Pope Adrian IV seeking permission to invade Ireland to “reform the church”. Ireland was already Catholic and not in need of reformation, but the Pope, who was also English, authorised Henry to invade Ireland under certain conditions. One such condition was that Ireland and all other Christian Islands came under the jurisdiction of the Pope. Since this therefore included England, King Henry did not invade at that time.

In 1166 MacMorrough, a claimant for one of the other Irish kingdoms (Leinster) was exiled and fled to Normandy. Here he obtained permission from King Henry to use the King’s English subjects to regain his kingdom. In 1167 he gained the support of the “Cambro-Norman” lord Richard “Strongbow” de Clare. Strongbow agreed to invade Ireland and restore MacMurrough to the throne of Leinster, but only after being promised MacMurrough’s daughter in marriage and his crown after his death In 1169 the main force of Norman and Welsh mercenaries arrived, quickly captured key towns, and restored the kingdom of Leinster. Richard de Clare married into the Irish family and by doing so became heir to that kingdom.

Once the Normans had conquered the majority of Ireland, Henry II arrived with 4,000 well armed men to quell any chance of Strongbow creating his own independent kingdom. All of the Norman knights, as well as the Vikings and the Gaels, capitulated and paid homage to Henry. The Treaty of Windsor was signed in 1175 under which Henry assumed control of the lion’s share of the conquered lands and the Norman mercenaries were awarded large estates.

In 1189 Henry appointed his 17 year old son, John, to be “Lord Protector of Ireland”. Under his “protection” the Norman Barons stole huge tracts of land from the remaining Gaelic clans, rendering the Treaty of Windsor worthless. In the same year Henry II died, leaving the throne to his eldest son, Richard the Lionheart (r. 1189-99). Although Richard was a master soldier, he was a dismal failure as a king. Incredibly, he conceded that the English monarchy was subservient to Philip II of France and his successors. Upon Richard’s death, his younger brother John I (r. 1199-1216) assumed the throne.

By the year 1204, John had lost a war with King Philip II of France, thereby losing all of his continental possessions including Normandy, Brittany, and Anjou. His weak reign allowed for the Norman Irish and the native Gaelic clans to enjoy a reprieve of several centuries from the meddling influence of London.

The Normans were excellent soldiers and ambitious castle builders. Everywhere they settled they left stone towers and keeps as evidence. They brought the concept of towns to Ireland, an idea that was alien to the native Gaels. However, what the Normans possessed in martial skills, they lacked in any identifiable culture. For some reason, the culture of Celtic Ireland suited them perfectly and they quickly adopted the language, dress, culture, and religion of their Irish adversaries.

By the year 1250, most of Ireland was controlled by the Normans. They clustered in towns and built fortified homes for defense. Although they usurped the Gaelic aristocracy, the common Irish continued to work the land and manage their livestock the same as they did before. Great stone churches were built by the Normans throughout Ireland and they remained great defenders of the Catholic faith, as well as their Gaelic compatriots.

The Irish system of gavelkind was replaced by the feudal system of the Normans. A stronger central government was established in Dublin, which greatly vexed the native Irish noblemen. Brehon Law was displaced by English common law, which in many ways was inferior to the Celtic system.

There were three culturally distinct regions in Ireland at this time.

“The Pale” was an area about 30 miles long and twenty miles wide surrounding the city of Dublin. This area was exclusively English and the people in the Pale considered themselves to be in an English colony.

Most of the island “beyond the Pale” consisted of many semi-autonomous fiefdoms ruled by the great Norman-Irish lords. Although these “aristocrats” were descended from the original Norman mercenaries, they gradually adopted most of the customs and language of Gaelic society.

The third region was known as “Gaelic Ireland”, and it encompassed western Ulster, Cork, and Kerry. It was the land of the O’Sullivan clan, the MacCarthy clan, and the O’Donoghue clan. It had never been conquered by the Normans and it remained fully independent of the feudal English society and its rule. The Gaelic lords, called the “Wild Irish” by Philip II, continued to enjoy a thoroughly Celtic hierarchy, along with its varied privileges and restrictions.

The Normans never completely subjugated Ireland. After a century of warfare, the Old Gaelic Order absorbed the Norman invaders and a period of relatively peaceful coexistence and assimilation began that lasted for nearly 250 years. When a second wave of English invaders arrived in Ireland in the sixteenth century they found that their Norman predecessors had become “more Irish than the Irish themselves”.

O’Sullivan History after the Norman invasion


In 1171, Dermot MacCarthy Mor, the king of Munster, officially submitted to Henry II, the first of the Irish Kingsto do so. This act seriously diminished his stature among his own people. Many Eoghanacht chiefs demanded that he abdicate in favor of the O’Sullivan Mor or some other MacCarthy chief. MacCraith, the oldest son of Buadhach, remained loyal to Dermot and refused to challenge him for the throne.

In 1192 MacCraith’s oldest son Donal Mor lost the family estate in the fertile “Golden Vale” to the invading Normans in 1192. The entire Eoghanacht nation, including the ruling MacCarthys, was forced to abandon its ancestral lands and begin the retreat that eventually led to the remote and desolate mountains of Cork and Kerry, the Third Milesian Migration. Many tribesmen of the time surmised that this great defeat of their people was a result of the MacCarthys, a cadet line of the royal blood of Milesius, being on the throne of Munster.The O’Sullivan family historians suggest that had the Eoghanacht chiefs been successful in wresting the throne away from Dermot in favor of Donal Mor the Eoghanacht nation may have been much better off. As it was, the proud race of Milesius was pushed into a spiraling descent that would end in merciless oppression and abject privation at the hands of their English overlords.




In 1196, Donal Mor’s brother, Gilla Padraig, was killed by the Normans in the Battle of Ferdruim, West Cork. Another brother of Donal Mor, Anad, was killed in 1201.

Giolla Mochoda, Donal’s son, was born in 1166. Giolla Mochoda’s name illustrates how deeply Christianity had penetrated Ireland by the twelfth century. It literally means, “Servant of Mochoda”. Mochoda was a saint that had preached in Munster. 1200    Giolla Mochoda was to be the next O’Sullivan Mor, and his son, Dunlong, born in 1200 would have succeded him. Giolla Mochoda had a younger brother Giolla na bhFlann.

By 1214 dissent was mounting against the McCarthy King of Munster who had pledged loyalty to the English King. Many Eoghanacht chieftains again demanded that the O’Sullivan Mor, Donal Mor assume his birthright as the king of Munster. At that time Donal Mor was living in Carrig between Clonakilty and Timoleague. Clonakilty is only 45 km by road from Baltimore, the birthplace of Timothy Sullivan some 600 years later. To eliminate the threat the McCarthy king invited Donal and all of his adult male children to a banquet at his stronghold in Raithin na nGaraidhthe in the territory of the Barretts in 1214. He then had the entire family treacherously murdered, including Giolla Mochoda. The only two survivors of the true senior line of the royal family of Milesius were Dunlong, Donal Mor’s 14 year-old grandson, and Giolla na bhFlann, Donal Mor’s youngest son, neither of whom attended the banquet.

Since Dunlong was the oldest son of Giolla Mochoda, and Giolla Mochoda was Donal Mor’s oldest son, Dunlong was the rightful heir to the title “The O’Sullivan Mor”. He and his supporters moved west to what is now known as County Kerry. Giolla na bhFlann, Dunlong’s uncle, settled with his supporters in Bantry and Berehaven in what is now County Cork. From Dunlong descend the O’Sullivan Mor and from Giolla na bhFlann descend the O’Sullivan Beara. The independence that the junior O’Sullivan Beara sept enjoyed from the senior O’Sullivan Mor tribe was a result of Dunlong being a minor at the time of the Eoghanacht invasion of Kerry. The evidence suggests that the O’Sullivans and the McCarthys were moving into the Iveragh peninsula around 1250.The "Beare" suffix came from the Beara peninsula that was named for the Spanish princess Bera, the wife of the first King of Munster


Gaelic Resurgence and Assimilation of the Normans (1270-1484)

The O’Sullivans continued to be harassed by the Normans and so allied themselves with the McCarthys and the O'DonoghuesIn 1259, John FitzThomas, with an illegitimate grant from the future king Edward I, then lord of Ireland, took by force the lands of the O’Sullivans and MacCarthys. By 1260, even the remote areas of Cork and Kerry were dotted with Norman castles and keeps. The Eoghanacht tribes, under the leadership of Finghin MacCarthy, continued to wage a guerilla war against the Normans. In order to finally wipe out any residual Gaelic supremacy over the area, FitzThomas assembled a large army and marched toward the Eoghanacht strongholds in the Cork and Kerry mountains. On July 24th, 1261, the Norman troops were ambushed and routed by the Irish in Callan Glen, near Kilgarvan, in the valley of the Roughty River. Many of the foreigners were slaughtered and all of the castles south of the River Maine were overtaken by the MacCarthys and O’Sullivans.

In 1261 the Norman Lord John Fitzthomas moved to wipe out all remaining Irish resistance in Cork and Kerry. However his army was ambushed and defeated by the Irish at the battle of Caisglin near Kilgarvan just north of Kenmare. The Irish were again victorious the following year, with the O’Sullivans and McCarthys subsequently taking over many Norman castles. These two battles settled the boundaries between the Normans of north Kerry (the FitzGeralds) and the three Gaelic families of south Kerry and west Cork. These boundaries were in effect for the next 300 years.

Over the following centuries there ensued an amazing Gaelic cultural resurgence and an associated Norman retreat. Between the mid thirteenth century and the mid fifteenth century, the native Gaelic lords reclaimed much of their lost territory and overwhelmed the Norman cultural influence on the island. There were four basic reasons for this reversal of fortune:

The first is that the Normans never had a sufficient number of settlers to preserve their military dominance over the Gaels.

The second is that the plague of 1349 disproportionately decimated the urban Norman populace and spared the less crowded rural Gaels. This further enhanced the advantage in numbers that the Gaels had over the invaders.

The third is that the culturally challenged Normans slowly became “Irish” themselves, rejecting the feudal system and the dominance of Dublin in favor of more regional freedom.

The fourth is that the Gaels learned from their foes and began to successfully employ Norman military tactics. This neutralized the martial advantage that the Normans once had over them.

Not only did the Gaelic order survive in Ireland, the Normans gradually were assimilated into it. They eventually adopted the Irish tongue, assumed the native dress, married Irish women, and co-opted many of the native customs.


O’Sullivans Through to the Second Invasion (1270 to 1535)

Dunlong, the son of the murdered Giolla Mochoda, the O’Sullivan Mor, fought his way into the Iveragh Peninsula in County Kerry and took control of Castles Dunloe, Dunkerron, Cappanacuss, and several other minor keeps.

Dunlong O’Sullivan Mor’s descendants were:

  • Murtagh O’Sullivan Mor born 1235;
  • Murtagh’s son, Bernard O’Sullivan Mor, born in 1270;
  • Bernard’s son Dunlong O’Sullivan Mor born in 1340;
  • Dunlong had two known sons, Cragh O’Sullivan Mor born in 1375, and Cragh’s younger brother, Rory O’Sullivan Mor.

Cragh was the last O’Sullivan of the senior Milesian line. When he died his son Donal O’Sullivan McCragh (born 1410) was still a minor, so his uncle Rory was elected the O’Sullivan Mor. Cragh’s widow and children had to leave Dunkerron castle and move to Cappanacuss Castle, a much smaller estate. As the family was large, many went abroad.

However Donal was still recognized as the senior line of the O’Sullivan clan, and became chief of the O’Sullivan McCragh sept. His title was the O’Sullivan McCragh, and he was the first of the O’Sullivan McCragh sept which is the oldest of the Irish Royal bloodlines.

The genealogy of Rory O’Sullivan Mor’s descendants is not kown in any detail. His bloodline continued in the O’Sullivan Mor leaders until The O’Sullivan Mor died without legitimate sons in 1768 and the O’Sullivan clan leadership reverted to the O’Sullivan McCragh sept.

Giolla na bhFlann, Dunlong’s uncle, settled with his supporters in Bantry and Bearehaven in what is now the Beara Peninsula in County Cork. Eventually they adopted the title of Lord of Beare and Bantry. They controlled Bantry, Cariganass and Dunboy castles. The O’Sullivan Beare resided in Dunboy Castle, built around 1473 by Lord Dermod O’Sullivan Beare near the tip of the Beara Peninsula near Castletownbere. This castle defended the harbor allowing the O’Sullivan Beare to control that part of the Irish Coast and collect sizeable taxes. Carriganass Castle was built in 1540 by clan chief Dermot O’Sullivan Beare.

The O’Sullivan Beare remained in control of their lands until the reigns of Elizabeth 1 and then Oliver Cromwell by which time they had either been killed of or fled into exile in Spain, France and America.

The Second Invasion.

From about 1300 through to the reign of Henry VIII the English royalty was more focussed on their domains in England, Scotland, Wales and France. Support for the Norman colonists in Ireland waned. The Irish lords took advantage and won back land. Consequently, the Norman colonists began to ally themselves more with the Irish than with England. These “Hiberno-Normans” began to adopt the Irish language and customs, intermarried with the Irish, and sided with the Irish in conflicts with England.

In 1535 the Hiberno-Norman Fitzgeralds, who had become the effective rulers of Ireland in the 15th century, openly rebelled against the crown. Henry VIII put down this rebellion and set about to pacify Ireland and bring it all under English government control, perhaps to prevent it being a base for foreign invasions of England (a concern that was to be sustained for another 400 or more years). Henry also decided to exercise his authority in Ireland by imposing his new religion of Anglicanism on the Catholic populace.

In 1541 Henry changed Ireland from a lordship to a full Kingdom, under the Lord Deputy of Ireland who was nominated by the King. With new institutions of government in place, the next step was to extend the control of the English Kingdom of Ireland over all of its claimed territory. Henry VIII's officials were tasked with extending the rule of this new Kingdom throughout Ireland, in the process either negotiating or fighting with the independent Irish Kings and lords. This took nearly a century to achieve, and the re-conquest was accompanied by a great deal of bloodshed, as it led to the assimilation – sometimes abolition – of lordships that had been independent for several hundred years. The re-conquest was completed during the reigns of Elizabeth I and James I, after many brutal and bloody conflicts.

Most of the surviving O’Sullivan leaders and nobility fled Ireland in the early part of the 17th century. Some settled in Spain which had sided with the Irish rebels, some in France, and some eventually immigrated to America.

The English had little success in converting the Irish to the Protestant religion. Doubtless the brutal methods used by the English to pacify the country and exploit its resources heightened resentment of English rule. Another reason may have been a determined proselytising campaign carried out in Ireland by counter-reformation Catholic clergy, many of whom had been educated in seminaries in Europe. Finally, the printing press, which had played a major role in disseminating Protestant ideas in Europe, came to Ireland very late.

From the mid-16th and into the early 17th century, English governments carried out a policy of colonisation known as Plantations. Scottish and English Protestants were sent as colonists to the various Irish provinces and counties, to settle land confiscated from the defeated Irish lords. These settlers, who had a British and Protestant identity, would form the ruling class of future British administrations in Ireland The largest of these projects, the Plantation of Ulster, had settled up to 80,000 English and Scots in the north of Ireland by 1641. The so-called Ulster Scots were predominantly Presbyterian which distinguished them from the Anglican English colonists.

In those early years of the 17th century, it looked possible for a time that with the immigration of English and Scottish settlers, Ireland could be peacefully integrated into British society. However, the continued discrimination by the English authorities against Irish Catholics on religious grounds ensured failure.

As examples a series of Penal Laws discriminated against all Christian faiths other than the established (Anglican) Church of Ireland. The principal victims of these laws were Roman Catholics and also, from the late 17th century on, adherents of Presbyterianism. From 1607, Catholics were barred from public office and from serving in the army. In 1615, the constituencies of the Irish Parliament were altered so that Protestants would form the majority in any given vote in the Irish House of Commons.

So in the wake of the Elizabethan conquest, the native Irish became defined by their shared religion, Roman Catholicism, in distinction to the new Protestant British settlers and the officially Protestant British government of Ireland. During the decades in between the end of the Elizabethan wars of conquest in 1603 and the outbreak of rebellion in 1641, Irish Catholics felt themselves to be increasingly threatened by and discriminated against by the English government of Ireland.

In 1641 Irish Catholics, threatened by expanding power of the anti-Catholic English Parliament, and with Scottish Covenanters also rebelling against King Charles I attempts to impose Anglicanism in Scotland, rebelled against English and Protestant domination. The Rising, launched in Ulster, provoked an outbreak of violence around the country, after which it was joined by most remaining Irish Catholic lords and their followers. In some respects, this rebellion was the end product of the long term alienation of Irish Catholics with English policies in Ireland. However, it was sparked off by the fear of impending civil war in the British Isles as a whole. The rebellion was marked by a number of massacres of Protestant settlers, particularly in Ulster, an event which scarred communal relations in Ireland for centuries afterwards.

As a result of the outbreak of the English Civil War in 1642, no English troops were available to put down the uprising and the rebels were left in control of most of Ireland. The Catholic majority briefly ruled the country and allied themselves with Charles I and the English Royalists. However, the Royalists were defeated by the Parliamentarians, Charles I was executed and Oliver Cromwell re-conquered Ireland in 1649–1653 on behalf of the English Commonwealth. The Cromwellian conquest of Ireland was marked by atrocities and brutality, and even worse was a scorched earth policy carried out by Parliamentarian commanders to subdue Irish guerrilla fighters, which caused famine throughout the country. This was particularly so in Beara and Bantry.

As punishment for the rebellion of 1641, almost all remaining lands owned by Irish Catholics were confiscated and given to British settlers. It has been calculated that up to a third of Ireland's population (4-600,000 people) died in these wars, either in fighting, or in the accompanying famine and plague. The Cromwellian conquest therefore left bitter memories in Irish popular culture. Included in the confiscations were the remaining O’Sullivan Mor lands in County Kerry which were granted to Sir William Petty.

Finally, in 1730 the English Crown in the reign of George II granted the remaining O’Sullivan lands in County Cork to the English Puxley family.

O’Sullivans After their Defeat

After their final defeat many of the O’Sullivans and other Irish Nobles went to Spain, France and America. This period was known as the flight of the earls. Both the French and the Spanish recognized the royal bloodlines of the O’Sullivans and gave them land, titles and generous pensions. A number of O’Sullivans served in the French army and Spanish navy. There are still two castles in France that are still the home of O’Sullivan descendants:

  • The O’Sullivan McCragh at Chateau du Gravier in Gravier, Cher, Centre Region.
  • The McMahon O’Sullivan Beare at Chateau de Sully, neare Beaune, Bourgogne Region.

The O’Sullivan McCragh sept as the senior O’Sullivan bloodline has continued until current times, with the current O’Sullivan clan chieftain from that sept.

The O’Sullivans were, as Dr MacCotter puts it, a ”fecund” clan. Clan chiefs could take multiple wives, and Brehon Law recognized all children as more or less legitimate. So the clan chief could have many offspring. Unfortunately, the genealogies concentrate on the clan nobility whether according to primogeniture or Tanistry. So for most Sullivans it will be unlikely that they can trace their genealogy back to Eochaid in the 9th century.

There are four main reference sources for this article:

O'Sullivan, The Earliest Irish Royal Family - History and Genealogy.

Author William Randolph McCreight. ISBN 978-0-8063-5647-1

Copy held by Richard Sullivan.


O'Sullivan - Irish Surname History Research. Video of a lecture to the O'Sullivan Clan Reunion, Sneem, County Kerry, Ireland 2013.

Author: Dr Paul MacCotter MA PHD, teacher in genealogy, family history, and medieval history at the University College Cork and the University of Limerick.

Copy held by Richard Sullivan


The O’Sullivan Clan Website at: