There’s something fascinating about the Irish last name heritage. Names like O’Fegan (Ó Fiacháin) and O’Dee (Ó Dé) carry centuries of history, with each one telling a unique story. Many of these last names have roots in ancient Irish clans, often linked to warriors, scholars, or poets. These names reflect not only a family’s heritage but also the broader cultural and historical landscape of Ireland.

We’ve gathered an extensive selection of Irish names, organized by theme. You might also find our feature on first names that start with O particularly interesting.

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Authentic Irish Last Names that Start with O

⭐ Our Favourite: O’Fegan (Ó Fiacháin)

Pronunciation: OH-FEE-gan
First recorded: 12th century
Meaning: The last name O’Fegan derives from the Irish Fiachán, meaning “raven” or “hawk.” It was likely given to a family known for their sharp vision or hunting prowess. The O’Fegans were part of the larger Uí Fhiachrach clan, which played a key role in the kingdom of Thomond. They were also known as skilled warriors and poets. Over time, many descendants migrated, with some settling in parts of North America.
Why it’s our favourite: This last name stands out due to its strong connection to nature and the symbolism of the raven or hawk, birds that represent keen insight and wisdom. The fact that the name was carried by warriors and poets makes it especially intriguing, as it encompasses both strength and intellect, giving a well-rounded sense of identity.

🍀 O’Bergin (Ó Beirgin)

Pronunciation: OH-BUR-gin
First recorded: 14th century
Region: Offaly
Meaning: O’Bergin is an ancient Gaelic name derived from “Beirgin,” meaning “little rock” or “small hill.” Historically, the O’Bergins were a sept closely tied to the O’Connors of Offaly, serving as hereditary stewards. Some scholars believe the name may have Norse influences, suggesting a Viking connection. The family was known for their stronghold in central Ireland, where they were involved in local governance and land stewardship.

🦁 O’Boland (Ó Beólláin)

Pronunciation: OH-BOH-land
First recorded: 11th century
Region: Mayo
Meaning: The last name O’Boland is linked to the Irish word beó meaning “lively” or “resilient.” It was borne by a medieval ruling family in Mayo, associated with the Uí Fiachrach dynasty. The Bolands were prominent warriors and later became landowners. The name remains common in Connacht, with descendants playing significant roles in Irish history and literature, including poets and scholars.

⚔️ O’Breslin (Ó Breisleáin)

Pronunciation: OH-BREZ-lin
First recorded: 1096
Region: Donegal
Meaning: Originating from the Gaelic Bresleán, meaning “descendant of Bresal,” this last name is tied to an early Irish chieftain. The O’Breslins were known for their role as hereditary poets and historians for the O’Donnells of Donegal. They maintained records of battles and noble lineages, preserving Irish oral traditions. Over time, they spread into Tyrone and Fermanagh, contributing to Ireland’s cultural heritage.

🏹 O’Callaghan (Ó Ceallacháin)

Pronunciation: OH-KAL-uh-han
First recorded: 12th century
Region: Cork
Meaning: O’Callaghan means “descendant of Ceallachán,” referring to a medieval king of Munster, Ceallachán of Cashel, who defended Ireland against Viking raids. The family held power in County Cork and were known as formidable warriors and landholders. The name remains prominent in Munster, with descendants playing influential roles in politics, literature, and sports.

🔥 O’Cahill (Ó Cathail)

Pronunciation: OH-KA-hill
First recorded: 10th century
Region: Galway
Meaning: Derived from Cathal, meaning “battle-mighty,” this name was associated with fierce warriors and chieftains. The O’Cahills were known for their military prowess and loyalty to the O’Connors of Connacht. Over time, the last name dispersed throughout Ireland, with notable descendants in both Ireland and the United States. The Cahills were involved in the Irish fight for independence and later became prominent figures in business and politics.

📖 O’Cassidy (Ó Caiside)

Pronunciation: OH-KAS-ih-dee
First recorded: 1172
Region: Fermanagh
Meaning: The O’Cassidys were hereditary physicians to the Maguires of Fermanagh, with their name deriving from Caiside, meaning “curly-haired.” They were one of the most learned medical families in medieval Ireland, writing treatises on medicine in Gaelic and Latin. Some Cassidy descendants played major roles in Irish poetry and music, and the name remains prominent in Ireland and America, especially among those with artistic or academic inclinations.

⚡ O’Colgan (Ó Colgáin)

Pronunciation: OH-KOL-gan
First recorded: 14th century
Region: Tyrone
Meaning: The name O’Colgan is derived from colg, meaning “sword” or “fierce.” The family historically served as warriors under the O’Neills of Ulster, known for their combat skills and leadership in battle. A notable bearer was John Colgan, a 17th-century Franciscan scholar who wrote extensively on Irish saints. The name is still found in parts of Ulster, particularly among families with deep historical roots.

🛡️ O’Connelly (Ó Conghaile)

Pronunciation: OH-KON-uh-lee
First recorded: 13th century
Region: Galway
Meaning: O’Connelly is linked to Conghalach, meaning “fierce as a hound.” This last name was associated with warriors of Connacht who served under Gaelic kings. The O’Connellys were landowners and military leaders, frequently clashing with Anglo-Norman settlers. The name has since spread worldwide, with many descendants becoming involved in politics, law, and business.

🌀 O’Coogan (Ó Cuagáin)

Pronunciation: OH-KOO-gan
First recorded: 16th century
Region: Kilkenny
Meaning: Derived from cuag, meaning “bent” or “winding,” O’Coogan may have originally referred to someone who lived near a twisting river or valley. The family was known for their craftsmanship and were skilled artisans in medieval Kilkenny, producing fine metalwork and stone carvings. Though less common today, the name remains associated with artistic and architectural heritage.

🌊 O’Coughlan (Ó Cochláin)

Pronunciation: OH-KOKH-lan
First recorded: 1014
Region: Offaly
Meaning: The O’Coughlans were a prominent Gaelic family who held lands in County Offaly. Their name comes from cochal, meaning “cloak” or “protection,” possibly referring to their role as defenders of the region. They were involved in the famous Battle of Clontarf in 1014, fighting against Viking invaders. Over time, the family played a key role in local governance, and the last name remains strong in central Ireland.

🌿 O’Cullen (Ó Cuilinn)

Pronunciation: OH-KUL-in
First recorded: 12th century
Region: Wicklow
Meaning: O’Cullen derives from cuilinn, meaning “holly.” The name was likely given to a family living near holly trees, which were considered sacred in ancient Ireland. The O’Cullens were known as skilled metalworkers and were associated with early monastic settlements. The name remains common in Leinster, with some branches migrating to Munster over time.

🌊 O’Dee (Ó Dé)

Pronunciation: OH-DEE
First recorded: 13th century
Region: Clare
Meaning: The last name O’Dee comes from the Irish Dé, meaning “god” or “divine.” It is believed to have originated among families who were early religious figures or scholars. The O’Dees were closely linked to monastic communities along the west coast, particularly in County Clare, where they were scribes and poets.

🔥 O’Deery (Ó Daighre)

Pronunciation: OH-DEER-ee
First recorded: 10th century
Region: Donegal
Meaning: Derived from daighre, meaning “fiery,” this last name was associated with a powerful warrior family in Ulster. The O’Deerys were known for their resistance to Norman incursions and held lands in Donegal for centuries. Some branches of the family later became storytellers and historians, preserving Gaelic folklore and history.

🏰 O’Devany (Ó Duibheannaigh)

Pronunciation: OH-DEHV-uh-nee
First recorded: 15th century
Region: Tyrone
Meaning: The name O’Devany is linked to dubh meaning “black” and eannaigh, meaning “marshy lands.” The family was prominent in County Tyrone, where they controlled fertile lands along riverbanks. A famous bearer, Cornelius O’Devany, was a Catholic bishop executed for his faith in the early 17th century, making the name significant in religious history.

⛰️ O’Davoren (Ó Duibhdábhoireann)

Pronunciation: OH-DAV-or-en
First recorded: 14th century
Region: Clare
Meaning: The O’Davorens were an esteemed family of brehons (judges) in medieval Ireland, known for their legal expertise. They were based in the Burren region of County Clare, where they compiled important Gaelic law texts. Their name is linked to dubh (black) and Bhoireann (the Burren), reflecting their origins.

⚔️ O’Deegan (Ó Duibhginn)

Pronunciation: OH-DEE-gan
First recorded: 11th century
Region: Laois
Meaning: Meaning “descendant of Duibhginn,” where dubh means “dark” and ginn could refer to birth or a person of importance, the O’Deegans were once a noble family in Leinster. They were warriors and landowners, frequently resisting English rule. Over time, they became farmers and merchants, but their history as defenders of Gaelic Ireland remains.

🌙 O’Duane (Ó Dubháin)

Pronunciation: OH-DOO-ane
First recorded: 12th century
Region: Galway
Meaning: O’Duane comes from dubh meaning “dark” or “black,” and may have referred to someone with dark hair or a connection to the night. The name was associated with poets and mystics in Connacht, particularly in Galway, where the family produced scholars and musicians. Some branches emigrated during the 19th century and became well-known in the arts abroad.

🛡️ O’Duggan (Ó Dubhagáin)

Pronunciation: OH-DOO-gan
First recorded: 14th century
Region: Tipperary
Meaning: O’Duggan comes from dubh meaning “black” and gán, meaning “little,” possibly referring to a small, dark-haired warrior. The family was historically tied to the O’Briens of Munster and served as advisors and military leaders. They were also historians, preserving accounts of medieval Irish battles.

🎯 O’Dwyer (Ó Dubhuir)

Pronunciation: OH-DWYE-er
First recorded: 10th century
Region: Tipperary
Meaning: Meaning “dark and swarthy,” the O’Dwyers were fierce warriors and defenders of Gaelic Ireland. They resisted English rule in the 17th century, fighting in multiple rebellions. The family held extensive lands in Munster until their forced displacement. Many O’Dwyers later became leaders in Irish-American communities.

🌾 O’Fahy (Ó Fathaigh)

Pronunciation: OH-FAH-hee
First recorded: 13th century
Region: Galway
Meaning: The last name O’Fahy derives from Fathach, meaning “giant” or “wise man,” suggesting the family’s early reputation for intelligence or stature. The O’Fahys were known as scholars and poets in Connacht, recording Irish history and mythology. Some branches later moved into politics, with descendants still prominent in Ireland today.

🌊 O’Fennell (Ó Fionnáin)

Pronunciation: OH-FEN-ell
First recorded: 13th century
Region: Waterford
Meaning: The name O’Fennell is derived from fionn, meaning “fair” or “blond-haired.” Historically, the family was closely associated with the coastal regions of Munster, particularly in Waterford and Limerick. The O’Fennells were involved in trade and fishing, with some members becoming influential merchants. The name remains common in the southeast of Ireland.

🍀 O’Finucane (Ó Fionnmhacháin)

Pronunciation: OH-FIN-oo-kan
First recorded: 14th century
Region: Clare
Meaning: O’Finucane comes from fionn (fair) and machán (possibly “son” or “descendant”). This last name was traditionally associated with County Clare, where the family served as poets and historians to the ruling Gaelic lords. The O’Finucanes were well-regarded for their knowledge of Irish law and literature. Some later became prominent in politics and business, particularly in Limerick.

⚔️ O’Fitzpatrick (Ó Maol Phádraig)

Pronunciation: OH-FITS-PAT-rick
First recorded: 11th century
Region: Laois
Meaning: One of the few Gaelic last names to retain the “Fitz” prefix (usually a Norman feature), O’Fitzpatrick means “descendant of Maol Phádraig,” referring to a devotee of St. Patrick. The family was originally part of the ruling septs in Ossory (modern-day Laois and Kilkenny), later becoming warriors and landowners. The name remains significant in Irish history, with descendants involved in the military and political affairs of both Ireland and Britain.

🔥 O’Fleadhbhair (Ó Flannabhra)

Pronunciation: OH-FLAN-av-ra
First recorded: 10th century
Region: Mayo
Meaning: The last name O’Fleadhbhair derives from Flannabhra, meaning “red eyebrows.” This suggests that early bearers of the name were known for their striking red hair. The family was historically connected to the western seaboard, serving as hereditary poets and historians in the courts of Connacht’s Gaelic kings. Some later branches of the family became known for their contributions to Irish literature.

🛡️ O’Gara (Ó Gadhra)

Pronunciation: OH-GAR-a
First recorded: 970 AD
Region: Sligo
Meaning: The O’Gara family descended from Gadhra, meaning “hound” or “warrior.” They were a powerful Gaelic dynasty in Connacht, ruling parts of modern-day Sligo and Mayo. The O’Garas were known for their military prowess, resisting Anglo-Norman incursions well into the 16th century. A famous bearer, Fearghal Ó Gadhra, was a 17th-century patron of Gaelic poetry.

🌿 O’Garvey (Ó Gairbhith)

Pronunciation: OH-GAR-vee
First recorded: 12th century
Region: Meath
Meaning: O’Garvey comes from Gairbhith, meaning “rough peace” or “mighty peace.” The family was originally part of the Uí Néill dynasty and held lands in Meath before being displaced by Norman settlers. They later spread to Ulster, where they became involved in local leadership. Some Garveys played notable roles in the Catholic resistance during the 17th century.

🏰 O’Grealish (Ó Grealais)

Pronunciation: OH-GREE-lish
First recorded: 15th century
Region: Galway
Meaning: O’Grealish is of Norman-Irish origin, likely deriving from a family that settled in Ireland and became Gaelicized. The name has strong connections to the Claddagh area of Galway, where the family was historically involved in fishing and maritime trade. Some members of the family became prominent shipbuilders, helping shape Ireland’s coastal economy.

🎭 O’Hanrahan (Ó hAnnracháin)

Pronunciation: OH-HAN-ra-han
First recorded: 16th century
Region: Wexford
Meaning: O’Hanrahan means “descendant of Annrachan,” a personal name of uncertain origin but possibly meaning “stormy” or “reckless.” The family was historically associated with Wexford, where they were landowners and political figures. Michael O’Hanrahan, an important figure in the 1916 Easter Rising, helped cement the name’s legacy in Irish nationalist history.

🦌 O’Hart (Ó hAirt)

Pronunciation: OH-HART
First recorded: 9th century
Region: Sligo
Meaning: O’Hart derives from Art, meaning “bear” or “noble one.” The family was part of the Uí Fiachrach dynasty, rulers of northern Connacht. They were known for their wisdom and governance, producing several influential scholars. John O’Hart, a 19th-century historian, is best known for his work tracing Irish genealogy.

🦅 O’Hession (Ó hOisín)

Pronunciation: OH-HESH-un
First recorded: 13th century
Region: Galway
Meaning: The last name O’Hession derives from Oisín, a legendary name meaning “little deer.” Oisín was a famous warrior-poet in Irish mythology, the son of Fionn MacCumhaill. The O’Hessions were traditionally poets and historians in Connacht, preserving the oral traditions of Gaelic Ireland. The family later became involved in political and clerical life, producing several prominent priests and educators.

🔥 O’Hurley (Ó hUrthuile)

Pronunciation: OH-HUR-lee
First recorded: 14th century
Region: Limerick
Meaning: O’Hurley is thought to derive from urthuile, meaning “flood” or “overflow.” The name may have originated with a family living near a major river. The O’Hurleys were an influential Munster family, many of whom became soldiers and clergymen. Dermot O’Hurley, Archbishop of Cashel, was martyred in 1584 for refusing to renounce Catholicism, making the name historically significant.

⚔️ O’Keane (Ó Catháin)

Pronunciation: OH-KEEN
First recorded: 11th century
Region: Derry
Meaning: O’Keane comes from Catháin, derived from cath, meaning “battle.” The family was historically associated with the northern Uí Néill and played an important role in Irish resistance to English rule. They were fierce warriors and chieftains, particularly in the regions of Derry and Antrim. The name remains common in both Ireland and among Irish diaspora communities.

🏰 O’Kinsella (Ó Cinnsealach)

Pronunciation: OH-KIN-se-la
First recorded: 12th century
Region: Wexford
Meaning: The last name O’Kinsella means “descendant of Cinnsealach,” a name meaning “proud-headed” or “chiefly.” The family was part of the Uí Ceinnsealaigh, a powerful ruling dynasty in Leinster. They were known for their resilience against Viking and Norman invasions. Today, the name remains particularly strong in Wexford and surrounding areas.

📜 O’Lennon (Ó Leannáin)

Pronunciation: OH-LEN-un
First recorded: 10th century
Region: Fermanagh
Meaning: O’Lennon comes from Leannán, meaning “lover” or “sweetheart,” and was often associated with poets and scholars. The O’Lennons were hereditary bards and historians in medieval Ireland, serving noble families such as the Maguires. The name later spread throughout Ulster and remains a well-known last name, with some famous bearers including musicians and writers.

🦁 O’Lyons (Ó Laighin)

Pronunciation: OH-LY-uns
First recorded: 12th century
Region: Galway
Meaning: The last name O’Lyons is derived from Laighin, meaning “warrior of Leinster.” The family originally held lands in the west of Ireland and were known for their leadership in local conflicts. Over time, the O’Lyons played roles in both trade and governance, with some branches of the family moving into the legal and academic professions.

🌊 O’Maney (Ó Mainnín)

Pronunciation: OH-MAN-ee
First recorded: 15th century
Region: Galway
Meaning: O’Maney comes from Mainnín, meaning “little monk,” possibly referring to a religious ancestor. The family was closely associated with monastic communities in Galway and Mayo, producing many scholars and priests. The name was later found among fishermen and traders along the western coast, emphasizing their deep connection to the sea.

🛡️ O’Molloy (Ó Maolmhuaidh)

Pronunciation: OH-MUL-oy
First recorded: 9th century
Region: Offaly
Meaning: The O’Molloys were a powerful ruling family in the kingdom of Firceall (now Offaly). Their name means “noble chief” or “great chieftain,” reflecting their high status in Gaelic Ireland. The family fiercely resisted English incursions into the midlands and maintained their lands for centuries. Even today, Molloy remains a well-regarded name in Ireland.

🌿 O’Moylan (Ó Maoileáin)

Pronunciation: OH-MOY-lan
First recorded: 13th century
Region: Clare
Meaning: O’Moylan comes from maol, meaning “bald” or “tonsured,” often referring to a devotee of a saint. The family was linked to religious and scholarly traditions, particularly in the west of Ireland. Over time, they became landowners and officials, and today, the name remains common in Munster and parts of Connacht.

⚔️ O’Mulcahy (Ó Maolchatha)

Pronunciation: OH-MUL-KA-hee
First recorded: 12th century
Region: Limerick
Meaning: O’Mulcahy means “devotee of battle,” indicating a warrior lineage. The family was known for their role in defending Munster from external threats, including Viking raids. Later, they became involved in law and administration, with some members becoming influential judges and clerics. The last name is still found in Limerick, Cork, and Kerry.

🏰 O’Muldoon (Ó Maoldúin)

Pronunciation: OH-MUL-DOON
First recorded: 10th century
Region: Fermanagh
Meaning: O’Muldoon derives from Maoldúin, meaning “devotee of St. Dúin.” The name was associated with early Christian monastic traditions in Ulster. The O’Muldoons were prominent rulers in Fermanagh, holding power until the Anglo-Norman invasions. Their lands were later absorbed into the Maguire lordship, but the name persisted in the region, with descendants becoming military leaders and politicians.

🌿 O’Mullan (Ó Maoláin)

Pronunciation: OH-MUL-lan
First recorded: 12th century
Region: Derry
Meaning: Derived from Maoláin, meaning “little chief” or “tonsured one,” O’Mullan was historically a clerical name, with many family members serving in the church. The O’Mullans were also warriors, closely allied with the O’Neills of Ulster. They defended Derry during conflicts with the English, and some later migrated to Scotland and North America.

🛡️ O’Mullarkey (Ó Maoilearca)

Pronunciation: OH-MUL-AR-kee
First recorded: 13th century
Region: Roscommon
Meaning: The last name O’Mullarkey means “devotee of St. Earc.” The family was part of the Uí Maine, a powerful ruling dynasty in Connacht. They were known for their involvement in local governance, often serving as judges and administrators. Some branches of the family became poets and scholars, preserving Gaelic traditions well into the 19th century.

🔥 O’Mulrooney (Ó Maolruanaidh)

Pronunciation: OH-MUL-ROO-nee
First recorded: 11th century
Region: Tipperary
Meaning: Meaning “descendant of Maolruanaidh,” this last name is linked to an early Irish chieftain known for his military prowess. The O’Mulrooneys were heavily involved in the defense of Munster, often fighting against both English forces and rival Gaelic clans. The name later became associated with farming and rural communities, particularly in Tipperary and Clare.

🌊 O’Munnelly (Ó Maonghaile)

Pronunciation: OH-MUN-ell-ee
First recorded: 14th century
Region: Mayo
Meaning: O’Munnelly is derived from Maonghal, meaning “wealthy noble.” The family was historically associated with maritime trade along the western seaboard, playing an important role in the economic development of Connacht. The O’Munnellys also served as navigators and shipbuilders, with some branches becoming prominent in America and Australia.

📜 O’Shanahan (Ó Seanacháin)

Pronunciation: OH-SHAN-a-han
First recorded: 10th century
Region: Clare
Meaning: O’Shanahan comes from Seanachán, meaning “descendant of Seanach,” a name meaning “ancient” or “wise one.” The family was known for their role as hereditary historians and poets to the Gaelic lords of Munster. They played a crucial part in recording the history of the O’Briens of Thomond, ensuring their legacy lived on through Irish literature.

⚔️ O’Shanley (Ó Seanlaoich)

Pronunciation: OH-SHAN-lee
First recorded: 12th century
Region: Leitrim
Meaning: O’Shanley means “descendant of Seanlaoch,” with Seanlaoch meaning “old warrior.” The family was part of the Uí Briúin dynasty, known for their loyalty in battle. They were key allies of the O’Rourkes and played an active role in resisting English invasions. Many later became prominent in the Irish independence movement.

🦅 O’Shanaghan (Ó Seannacháin)

Pronunciation: OH-SHAN-a-gan
First recorded: 13th century
Region: Donegal
Meaning: Derived from Seannachán, meaning “little wise one,” this last name was traditionally associated with storytelling and scholarship. The O’Shanaghans were keepers of folklore, ensuring that myths and legends were passed down through generations. Some family members were also known as healers, using ancient herbal remedies in rural communities.

🎭 O’Sheerin (Ó Sírín)

Pronunciation: OH-SHEER-in
First recorded: 15th century
Region: Sligo
Meaning: O’Sheerin comes from Sírín, which is linked to sír (lasting or eternal), possibly meaning “descendant of the everlasting one.” The family was historically involved in religious and artistic circles, producing several well-known musicians and playwrights. The name became more widespread in the 18th century as many O’Sheerins emigrated abroad.

🏹 O’Tracy (Ó Treasaigh)

Pronunciation: OH-TRAY-see
First recorded: 9th century
Region: Limerick
Meaning: The last name O’Tracy is derived from Treasaigh, meaning “warlike” or “fighter.” The O’Tracys were renowned warriors in Gaelic Ireland, particularly in Munster, where they served as military leaders under the O’Briens. Some branches of the family later became involved in politics, playing key roles in Irish uprisings against British rule.

Last Names with a Strong Irish Influence

🌿 O’Banion (Ó Bánáin)

Pronunciation: OH-BAN-yun
First recorded: 14th century
Region: Offaly
Meaning: O’Banion is derived from bán, meaning “white” or “fair-haired,” possibly describing an ancestor’s appearance. The family was historically associated with Offaly, where they served as poets and scribes to Gaelic chieftains. Some branches migrated to Ulster, where the name evolved into variations like Banyan. The O’Banions played key roles in early Irish literature and education.

🐝 O’Behan (Ó Beacháin)

Pronunciation: OH-BEH-han
First recorded: 12th century
Region: Wexford
Meaning: Derived from beach, meaning “bee,” the last name O’Behan may have originally denoted a beekeeper or someone associated with honey production. The name is common in Leinster, particularly in Wexford, where the family was involved in agriculture and trade. Brendan Behan, the famous Irish playwright, is one of the best-known bearers of this last name.

🏰 O’Bodkin (Ó Bodacháin)

Pronunciation: OH-BOD-kin
First recorded: 13th century
Region: Galway
Meaning: The last name O’Bodkin is of Anglo-Norman origin but became fully Gaelicized. The Bodkins were one of the “Tribes of Galway,” a group of merchant families who controlled trade in medieval Ireland. The name may derive from bodach, meaning “peasant” or “rustic,” though the family rose to prominence as influential traders and landowners.

🔥 O’Brislane (Ó Breisleáin)

Pronunciation: OH-BRIZ-lan
First recorded: 15th century
Region: Donegal
Meaning: The last name O’Brislane likely originates from breisleán, meaning “ember” or “spark,” possibly referring to a fiery temperament or a blacksmithing heritage. The family was historically associated with Ulster and played a role in defending the region from English incursions. Some later emigrated to Scotland and America, where the name evolved into different spellings.

⚔️ O’Carney (Ó Cearnaigh)

Pronunciation: OH-KAR-nee
First recorded: 10th century
Region: Meath
Meaning: O’Carney comes from cearnach, meaning “victorious” or “warlike.” The family was once prominent warriors in the midlands, closely allied with the O’Neills. They were known for their involvement in battles against Norman invaders and later took part in Irish rebellions. Today, variations of the name can be found throughout Ireland and the Irish diaspora.

🌊 O’Clifford (Ó Clúmháin)

Pronunciation: OH-KLIF-ord
First recorded: 14th century
Region: Kerry
Meaning: O’Clifford is of Norman origin but became closely linked to Ireland, particularly in Kerry, where the family held lands. The Irish form Clúmháin is thought to mean “feathery” or “plumed,” possibly referring to heraldic symbols. The family was involved in maritime trade and some branches became prominent in English-Irish politics.

🛡️ O’Coghlan (Ó Cochláin)

Pronunciation: OH-KOKH-lan
First recorded: 11th century
Region: Offaly
Meaning: O’Coghlan comes from cochal, meaning “cloak” or “protection,” possibly referring to a defensive role in battle. The family was historically powerful in the midlands, ruling over territories in Offaly. They were known for their resilience against English expansion and played key roles in preserving Gaelic traditions.

📜 O’Cowley (Ó Cobhthaigh)

Pronunciation: OH-COW-lee
First recorded: 12th century
Region: Westmeath
Meaning: The last name O’Cowley is derived from cobhthach, meaning “victorious” or “triumphant.” The family served as poets and scholars to Gaelic lords, particularly in the midlands. Some members of the O’Cowley family became prominent clerics, contributing to Irish religious and literary history.

🦅 O’Culligan (Ó Cuileagáin)

Pronunciation: OH-KUL-ih-gan
First recorded: 13th century
Region: Clare
Meaning: O’Culligan is thought to come from cuileag, meaning “little fly” or “nimble one,” possibly referring to agility or swiftness. The family was historically linked to Clare, where they were skilled horsemen and messengers. Some branches later became involved in Irish resistance movements against British rule.

🎭 O’Dalton (Ó Dáltún)

Pronunciation: OH-DAL-tun
First recorded: 10th century
Region: Westmeath
Meaning: The last name O’Dalton is of Anglo-Norman origin but became deeply integrated into Gaelic society. The D’Altons were granted lands in Ireland after the Norman invasion and later adopted Irish customs and language. The name means “descendant of the fostered one,” as dáltún relates to fostering, an important aspect of medieval Irish society.

⛰️ O’Davoran (Ó Duibhdábhoireann)

Pronunciation: OH-DAV-or-an
First recorded: 14th century
Region: Clare
Meaning: The O’Davorans were a renowned family of Brehon (legal) scholars in medieval Ireland, particularly in the Burren region of Clare. The name likely derives from dubh (black) and Bhoireann (the Burren), indicating an ancestral connection to the rugged limestone landscape. The family played a key role in preserving Gaelic law and contributed to early Irish legal manuscripts.

🌿 O’Drennan (Ó Draighnáin)

Pronunciation: OH-DREN-an
First recorded: 12th century
Region: Kilkenny
Meaning: O’Drennan comes from draighean, meaning “blackthorn,” a tree often associated with resilience and protection. The family was historically known as farmers and landowners in the southeast of Ireland. They played a role in local politics and administration, with some branches later migrating to America and Australia.

🏹 O’Fallon (Ó Fallamhain)

Pronunciation: OH-FAL-on
First recorded: 10th century
Region: Roscommon
Meaning: The O’Fallons were an influential family in Connacht, serving as chieftains and warriors. Their name derives from fallamhan, meaning “superiority” or “leader.” The family was closely allied with the O’Connors, kings of Connacht, and were key figures in medieval Irish military campaigns. Today, the name is common in both Ireland and the Irish diaspora.

⚔️ O’Fearon (Ó Fearáin)

Pronunciation: OH-FAYR-on
First recorded: 13th century
Region: Armagh
Meaning: O’Fearon comes from fear (man), with fearán meaning “little man” or “warrior.” The family was closely associated with the O’Neills and played an active role in defending Gaelic Ulster. They were prominent in local governance, and some later became involved in Irish revolutionary movements.

🔥 O’Fenton (Ó Fionntáin)

Pronunciation: OH-FEN-ton
First recorded: 14th century
Region: Cork
Meaning: The last name O’Fenton comes from Fionntán, meaning “little fair one” or “bright one.” The Fentons were originally Norman settlers who became fully Gaelicized. They were involved in trade and politics in Munster, with several members serving as influential merchants in Cork. The name later spread throughout the British Isles.

🌊 O’Glynn (Ó Glinn)

Pronunciation: OH-GLIN
First recorded: 12th century
Region: Waterford
Meaning: O’Glynn derives from gleann, meaning “valley,” indicating a family originally from a river valley or glen. The family held lands in Waterford and Tipperary and were known for their expertise in forestry and agriculture. Some O’Glynns became prominent church figures, contributing to early Irish Christian history.

🏰 O’Grealish (Ó Grealais)

Pronunciation: OH-GREE-lish
First recorded: 15th century
Region: Galway
Meaning: The O’Grealish family, possibly of Norman origin, became fully integrated into Gaelic society. Their name may derive from grealach, meaning “gravelly ground.” They were historically involved in fishing and maritime trade, particularly in the Claddagh area of Galway. Many O’Grealish descendants played key roles in local business and politics.

🛡️ O’Houlihan (Ó hUallacháin)

Pronunciation: OH-HOO-lih-han
First recorded: 10th century
Region: Kerry
Meaning: O’Houlihan comes from uallach, meaning “proud” or “noble.” The family was associated with Munster’s warrior class and served as military leaders under Gaelic kings. The name remains common in Kerry, with some branches producing poets, historians, and even prominent actors.

📜 O’Haniffy (Ó hAinbhith)

Pronunciation: OH-HAN-ih-fee
First recorded: 11th century
Region: Galway
Meaning: The last name O’Haniffy is linked to Ainbhith, meaning “stormy” or “wild.” Historically, the family was known for its association with seafaring and weather lore, playing a role in coastal communities in Galway. Some O’Haniffys were also renowned healers, using traditional Gaelic medicine.

🎭 O’Harahan (Ó hÁrcháin)

Pronunciation: OH-HAR-a-han
First recorded: 13th century
Region: Limerick
Meaning: The last name O’Harahan likely comes from Árchán, meaning “chief” or “leader.” The family held influence in Munster and were known for their involvement in Irish music and storytelling. Some later emigrated and became well-known figures in arts and literature.

🍀 O’Healy (Ó hÉilidhe)

Pronunciation: OH-HEE-lee
First recorded: 12th century
Region: Tipperary
Meaning: The last name O’Healy comes from Éilidhe, meaning “descendant of Éilidh,” a name associated with “the bright one” or “radiant.” Historically, the O’Healys were a prominent family in Tipperary, serving as chieftains and warriors. Their lands were rich in agricultural potential, and the family was influential in local governance and military affairs. Some members were also skilled in medicine, contributing to the family’s long-standing importance in the region.

🦅 O’Hooligan (Ó hUallacháin)

Pronunciation: OH-HOOL-i-gan
First recorded: 14th century
Region: Kilkenny
Meaning: O’Hooligan is derived from uallach, meaning “proud” or “noble.” This last name was likely used for a warrior family that held a prominent position in Gaelic society. The O’Hooligans were known for their resistance to English rule, with some of the family later emigrating to America. The name remains notable in Irish-American culture, often associated with larger-than-life personalities.

🎉 O’Joys (Ó Laoighis)

Pronunciation: OH-JOYZ
First recorded: 16th century
Region: Galway
Meaning: O’Joys is derived from Laoighis, meaning “warrior” or “hero.” The name signifies a family involved in both military and cultural pursuits. The O’Joys were well-known as skilled bards and historians, recording important events for the Gaelic kings of Connacht. Some branches of the family migrated to America, where the last name became associated with vibrant Irish-American communities.

🏹 O’Kivlehan (Ó Cibhleacháin)

Pronunciation: OH-KIV-lan
First recorded: 12th century
Region: Clare
Meaning: O’Kivlehan derives from cibhleachán, meaning “descendant of Cibhleachán,” which itself comes from cibhleach meaning “mighty” or “powerful.” The family was originally based in Clare, where they were part of the larger Gaelic warrior class. Known for their strength and leadership, they resisted English attempts to encroach on their lands. The O’Kivlehans were also recognized for their contributions to local governance.

🌿 O’Leighlin (Ó Lachtnáin)

Pronunciation: OH-LAY-lin
First recorded: 11th century
Region: Carlow
Meaning: O’Leighlin is derived from Lachtnán, a personal name that means “bright” or “radiant.” The family was historically associated with the region of Carlow, where they were involved in religious and political matters. The O’Leighlins held estates in the area, and some branches were later involved in the Gaelic wars against English forces. Their name lives on in several Irish-American communities.

🏞️ O’Loughney (Ó Luachna)

Pronunciation: OH-LOKH-nee
First recorded: 13th century
Region: Louth
Meaning: The last name O’Loughney comes from Luachna, meaning “descendant of Luach,” which is believed to refer to a person of noble or high birth. The family was historically involved in trade and landholding in Louth. The O’Loughneys were known for their ties to the O’Connors and played an important role in the social structure of medieval Ireland.

🦉 O’Lunn (Ó Luinín)

Pronunciation: OH-LUN
First recorded: 14th century
Region: Kerry
Meaning: O’Lunn comes from Luinín, meaning “descendant of Luin,” a name linked to “warrior” or “champion.” The family was active in defending Gaelic Ireland from English settlers. They held land in Kerry and played an important part in local conflicts. Over time, O’Lunn became a name associated with resilience, bravery, and strength.

🏰 O’Maher (Ó Meachair)

Pronunciation: OH-MAH-her
First recorded: 10th century
Region: Tipperary
Meaning: O’Maher is derived from Meachair, meaning “plain” or “level ground.” The O’Mahers were originally a landholding family in Tipperary and were known for their involvement in farming and local politics. They also served as military leaders, defending Munster from external threats. Over the centuries, the family spread to other parts of Ireland and the Irish diaspora.

🌊 O’Mannin (Ó Mainnín)

Pronunciation: OH-MAN-in
First recorded: 13th century
Region: Galway
Meaning: O’Mannin is derived from Mainnín, meaning “little monk” or “one who is devoted.” The family was associated with religious life, particularly in the region of Galway, where they were known for their scholarly work. Some members of the family later became influential priests and monks, contributing to the spread of Christianity in Ireland.

🎭 O’Melia (Ó Maoile)

Pronunciation: OH-MEE-lee-ah
First recorded: 15th century
Region: Cork
Meaning: O’Melia comes from Maoile, meaning “devotee” or “follower.” The family was associated with the region of Cork, where they were known as patrons of the arts and literature. Many O’Melias were involved in the literary tradition, producing works that preserved Irish culture and history. The name is also associated with scholarly and religious figures.

🌿 O’Mongan (Ó Mongáin)

Pronunciation: OH-MON-gan
First recorded: 13th century
Region: Clare
Meaning: O’Mongan is derived from Mongán, meaning “little monk” or “devotee.” The family was linked to the early Christian era, where monasticism was central to Irish life. The O’Mongans were known for their religious and scholarly pursuits, particularly in County Clare, where they contributed to preserving Irish history and traditions. Their influence continued for centuries, with some later descendants being prominent in religious roles.

🏰 O’Mullane (Ó Maoláin)

Pronunciation: OH-MUL-lan
First recorded: 12th century
Region: Cork
Meaning: The last name O’Mullane comes from Maolán, meaning “little chief” or “devotee.” The family was part of the Gaelic nobility in Munster, with a strong presence in Cork. They were known for their military strength and close ties to the O’Briens. The O’Mullanes were also important figures in Irish poetry and legal traditions, preserving Gaelic heritage for generations.

⚔️ O’Murnane (Ó Murnáin)

Pronunciation: OH-MUR-nan
First recorded: 14th century
Region: Limerick
Meaning: O’Murnane is derived from Murnán, meaning “little protector” or “guardian.” The family was known for its role as protectors of the land and defenders of local Irish territories in Limerick. The O’Murnanes were associated with local governance, particularly in the southwestern part of Ireland, and became important figures during the turbulent times of Irish resistance to Norman rule.

🦅 O’Nelis (Ó Niallais)

Pronunciation: OH-NELL-iss
First recorded: 11th century
Region: Tyrone
Meaning: O’Nelis is derived from Niall, meaning “champion” or “cloud,” referencing an ancient Gaelic king, Niall of the Nine Hostages. The family is part of the powerful O’Neill dynasty and was historically dominant in Ulster, particularly Tyrone. O’Nelis played significant roles in the military and political life of medieval Ireland, with descendants involved in various rebellions and the fight for Irish independence.

🐉 O’Raverty (Ó Robhartaigh)

Pronunciation: OH-RAH-ver-tee
First recorded: 12th century
Region: Armagh
Meaning: The last name O’Raverty comes from Robhartach, meaning “a brave person” or “warrior.” The O’Ravertys were part of the Uí Néill dynasty and served as protectors and warriors in the region of Armagh. They were known for their role in defending Ireland against Viking invasions and later Norman settlers. The name carries a sense of strength and valor that continues to resonate today.

🏞️ O’Reape (Ó Riabhaigh)

Pronunciation: OH-REE-uhp
First recorded: 13th century
Region: Galway
Meaning: O’Reape comes from Riabhaigh, meaning “one who has a rough or wild nature.” The family originated in Galway and was associated with the local Gaelic nobility. The O’Reapes were known for their role in both military and political life, resisting English rule while contributing to Irish culture through poetry and music. The name endures as a mark of Irish resilience and strength.

🍃 O’Scullane (Ó Scolláin)

Pronunciation: OH-SKULL-ane
First recorded: 14th century
Region: Kerry
Meaning: O’Scullane is derived from Scollán, meaning “little scholar” or “student.” The family was deeply connected to the intellectual and religious life of medieval Ireland, particularly in Kerry. They were renowned for their role in preserving Irish culture through the study of the Gaelic language and history. Some O’Scullanes later became prominent figures in the church and academia.

🎭 O’Shine (Ó Seighin)

Pronunciation: OH-SHINE
First recorded: 12th century
Region: Donegal
Meaning: The last name O’Shine is derived from Seighín, meaning “little saint.” The O’Shines were known for their connection to both the ecclesiastical and military worlds. In Donegal, they played key roles in defending local Gaelic territories. They also contributed to the religious life of the region, with several members becoming monks and priests in Ireland and beyond.

🦉 O’Tagh (Ó Taidhg)

Pronunciation: OH-TAH
First recorded: 10th century
Region: Kerry
Meaning: O’Tagh comes from Taidhg, meaning “poet” or “philosopher.” The O’Taghs were famous for their involvement in the arts, particularly in the poetic tradition, and were part of the intellectual elite of ancient Ireland. In Kerry, they were influential in preserving Irish literature and mythology, passing down stories and songs that would shape the country’s culture for generations.

🌿 O’Tanney (Ó Tonnaigh)

Pronunciation: OH-TAN-ee
First recorded: 11th century
Region: Cork
Meaning: O’Tanney is derived from Tonnach, meaning “descendant of the wave” or “storm.” The name reflects the family’s connection to the sea, as many O’Tanneys were involved in maritime trade and fishing. Based in Cork, they also played roles in local governance and resistance to English rule, with some later emigrating to the United States and maintaining their cultural ties.

🌿 O’Tomney (Ó Tomhnaigh)

Pronunciation: OH-TOM-nee
First recorded: 12th century
Region: Meath
Meaning: The last name O’Tomney comes from Tomhnaigh, which means “descendant of Tomán,” a name derived from tomhach, meaning “hill” or “mound.” The O’Tomneys were traditionally associated with the fertile lands of Meath, where they played significant roles in local governance and military affairs. The family was known for its involvement in both agriculture and military leadership, defending their lands from external threats. Over time, O’Tomney became a name associated with resilience, and some members of the family migrated abroad, particularly to America, where the name still carries strong Irish cultural ties.

Over the centuries, Irish names have evolved while still holding onto their deep cultural roots – explore our collections of first and last names to find one that carries true meaning.