Irish surnames starting with M

The M names in brief

• MacDermot · Mac Diarmada · Gaelic dynasty
  Son of Diarmaid. The MacDermots of Moylurg were a branch of the Síol Muireadhaigh, the ruling race of Connacht, and next to the O'Connors its most powerful family; they descend from Maolruanaidh, son of Tadhg O'Connor, King of Connacht in the 11th century, and take the name from his grandson Diarmaid, who died in 1159. In the mid-14th century they split into three septs: MacDermot of Moylurg, overlord of them all, with his fortress on the Rock of Lough Key near Boyle; MacDermot Roe of Tír Thuathail, at Alderford; and MacDermot Gall of Airtech.
• MacNamara · Mac Conmara · Gaelic sept
  Son of Cú Mara, 'hound of the sea'. Cú Mara means hound of the sea. Next to the O'Briens, the MacNamaras were the most powerful of the Dál gCais.
• Madden · Ó Madáin · Gaelic sept
  Descendant of Madán (from madadh, 'hound'). Madadhán is a pet form of madadh, a dog, and the O'Maddens were a distinguished branch of the Uí Maine in Galway, of the same stock as the O'Kellys, descended from Madadhán, slain in 1008, son of Gadhra Mór, chief of Uí Maine from 1014 to 1027. About the middle of the 11th century their district, Síol nAnmchadha, became independent, and its chieftaincy stayed in the family almost unbroken until the middle of the 17th century.
• Madigan · Ó Madagáin · Gaelic sept
  The same as Ó Madáin (Madden). An offshoot of the O'Maddens of Galway, Woulfe writes, who settled in Clare and Limerick in the 16th century and were still numerous there.
• Magee · Mag Aoidh · Gaelic sept
  Son of Aodh, 'fire'. Mag Aodha, son of Aodh: a very common surname in Ulster, where Woulfe believes there were several families of different origin under the name. One family were chiefs of Muinntear Tlamáin in Westmeath.
• Maguire · Mag Uidhir · Gaelic dynasty
  Son of Odhar, 'the dun-coloured'. Mag Uidhir, son of Odhar, the pale or dun-coloured one: the name of a great Fermanagh family, once among the most powerful in Ulster. Woulfe finds it first in the Annals at the year 956.
• Maher · Ó Meachair · Gaelic sept
  Descendant of Meachar, 'hospitable'. Meachar means hospitable. The O'Meaghers were a Tipperary family of the same stock as the O'Carrolls of Ely, lords of Uí Cairín, the barony of Ikerrin at the foot of the Devil's Bit, with their seat at Druim Saileach, where the castle of Moydrum stands south of Roscrea.
• Malone · Ó Maoileoin · Gaelic learned family
  Descendant of Maoileoin, 'devotee of St John'. An ecclesiastical family of Clonmacnoise, where several of them were abbots — a name that belonged to the monastery on the Shannon before it belonged to anyone else.
• Mangan · Ó Mongáin · Gaelic septs (several)
  Descendant of Mongán, a diminutive of mongach, ‘hairy’. At least three distinct families bore the name, Woulfe writes, seated in Cork, Mayo and Fermanagh. In the 16th century it was also found in Galway, Clare, Kerry, Tipperary, Kildare and Wexford.
• Mannion · Ó Mainnín · Gaelic sept
  Descendant of Mainnín — perhaps the same as Mainchín. Chiefs of Sodhan, a district nearly the same as the barony of Tiaquin in Galway. Woulfe notes Ó Mainnín, King of Sodhan, in the Chronicon Scotorum as early as 1135; the chief lived at Menlough Castle, and the clan held together until the time of James I.
• Martin · Mac Giolla Mháirtín / Máirtín · Gaelic sept & Norman tribe
  Devotee of St Martin. Máirtín, son of Martin. Woulfe notes that there are many separate families of the name in Ireland, of whom the most distinguished were the Martyns, one of the Tribes of Galway.
• Masterson · Mac an Mháighistir · Gaelic sept & English settlers
  Son of the master, from máighistir (Latin magister). The name seems to have begun in Co. Cavan, Woulfe writes, and by the end of the 16th century it had spread into Longford and Roscommon.
• McAleer · Mac Giolla Uidhir · Gaelic sept / also Scottish
  Son of Giolla Odhar, ‘the pale youth’. A rare Armagh surname, Woulfe writes. Eachdonn Mac Giolla Uidhir was Primate of Armagh early in the 13th century.
• McAllister · Mac Alastair · Scottish Gaelic (a MacDonald branch)
  Son of Alastar, a Gaelic form of Alexander. ‘Son of Alastar’, the Gaelic form of Alexander. Woulfe says it was the name of a branch of the MacDonalds, long settled in Co.
• McAndrew · Mac Aindriú · Norman-Gaelic (Barretts) / Scots (Ross)
  Son of Andrew. In Mayo this is an Irish patronymic taken by a branch of the Barretts of Tirawley, a Norman family. Woulfe says they were seated in the district called the Two Bacs, between Lough Conn and the River Moy, and that the name was very common there.
• McArdle · Mac Árdghail · Gaelic sept
  Son of Árdghal, ‘high valour’. A well-known south Ulster surname, Woulfe writes. The family is probably a branch of the MacMahons.
• McBride · Mac Giolla Bhríde · Gaelic sept
  Son of the servant of St Brigid. A Donegal name from the Rosses and Gweedore, carried to Kintyre in Scotland and back again. Maud Gonne MacBride's married name, and John MacBride was executed after the Rising of 1916.
• McCabe · Mac Cába · Scots-gallowglass
  Son of Cába. Mac Cába, perhaps from cába, a cap or hood. A military family of Norse origin from the Hebrides, a branch of the MacLeods according to MacFirbis, who came to Bréifne in the 14th century as captains of gallowglasses to the O'Rourkes and O'Reillys; the Four Masters first mention them in 1358.
• McCaffrey · Mac Gafraidh · Gaelic sept
  Son of Godfrey. A branch of the Maguires of Fermanagh, Woulfe writes, and by his day common in Ulster. It should not be confused with Mac Eachmharcaigh, which sometimes took the same English form.
• McCann · Mac Cana · Gaelic sept
  Son of Cana, 'wolf cub' — a young warrior. Lords of Cinel Aonghusa, or Clann Breasail, on the south side of Lough Neagh in County Armagh. Still one of the county's commonest names.
• McCarthy · Mac Cárthaigh · Gaelic dynasty
  Son of Cárthach, 'loving'. Cárthach is an ancient name meaning loving. The MacCarthys were the chief family of the Eóganacht, descendants of Eoghan Mór, son of Oilioll Olum; they take their name from Cárthach, lord of the Eóganacht, whose death in 1045 is in the annals, a great-grandson of Ceallachán of Cashel.
• McConnell · Mac Conaill · Gaelic sept & Scottish
  Son of Conall — 'hound' and 'valour'; in Ulster also from Mac Dhòmhnaill. Two names in one: a Gaelic Irish Mac Conaill, and the Scots MacDonnells who crossed to Antrim as gallowglass and later as settlers.
• McCormack · Mac Cormaic · Gaelic sept
  Son of Cormac, 'charioteer'. Mac Cormaic, son of Cormac, an ancient and very common Irish personal name, and so, Woulfe says, a common surname in every part of Ireland. The tenor John McCormack was born in Athlone.
• McCullough · Mac Cú Uladh · Gaelic sept
  Son of Cú Uladh, 'the Hound of Ulster'. In Ireland this name is often Mac Con Uladh, son of Cú Uladh, the hound of Ulidia or east Ulster — an east Ulster surname, and Woulfe notes forms such as MacAnulla, MacNully and MacCullow. Many Ulster McCulloughs are of Scottish origin, a separate name.
• McDaid · Mac Daibhéid · Gaelic sept
  Son of Davet, a diminutive of David. A branch of the O'Dohertys of Inishowen, taking their name and descent from David O'Doherty, who fell in battle in 1208. Woulfe says they were numerous in north-west Ulster, where the name is usually written MacDaid or MacDevitt.
• McDonagh · Mac Donnchadha · Gaelic sept
  Son of Donnchadh. Mac Donnchadha, son of Donnchadh. Woulfe gives three families: a branch of the MacCarthys, chiefs of Duhallow in Cork, with their seat at Kanturk; a branch of the MacDermots of Moylurg, chiefs of Tirerrill and Corran in Sligo, who lived at Ballymote and under whose patronage the Book of Ballymote was compiled, with an offshoot in Clare and Limerick; and a Scottish clan in Perthshire, who became Duncans.
• McDonnell · Mac Dónaill · Scots-Gaelic
  Son of Dónall. Mac Domhnaill, son of Domhnall, world-mighty. Most Irish MacDonnells belong to the MacDonalds of Scotland, Lords of the Isles and the most powerful of the Highland clans, who came to Ireland in large numbers in the 14th and 15th centuries as leaders of gallowglasses and settled in Leinster and elsewhere.
• McElroy · Mac Giolla Rua · Gaelic sept
  Son of the red-haired youth. Son of the giolla rua, the red-haired youth. The head of the family lived at Ballymackilroy in the parish of Aghalurcher, near Lough Erne, and left the name on the map there.
• McEvoy · Mac Fhíodhbhuidhe · Gaelic sept
  Son of Fíodhbhadhach, ‘of the wood, woodman’. A family in Laois, Woulfe writes, who were anciently chiefs of Tuath Fiodhbhuidhe, apparently in the barony of Stradbally. In Ulster many MacAvoys and MacEvoys are really Mac an Bheatha (McVeigh), whose English forms tended to be made to match this name.
• McFadden · Mac Pháidín · Scots-Gaelic & Irish
  Son of Páidín, 'little Patrick'. A name of Kintyre origin, well known across Ulster and in Mayo. In Donegal it took root deeply enough around Gweedore and the Rosses to read as thoroughly Irish.
• McGahey · Mag Eachaidh · Gaelic sept
  Son of Eochaidh, ‘rich in cattle’. Woulfe calls this an Ulster variant of Mag Eochadha, which is itself a form of Mac Eochadha, the name usually written Keogh. He describes the Keogh families under Mac Eochadha (in Leinster, Roscommon and Tipperary) but gives the Ulster McGaheys no history of their own.
• McGale · Mac Cathail / Mac Cathmhaoil · Gaelic sept
  Son of Cathal, 'battle-mighty' — or of Cathmhaol, 'battle-chief'; the authorities differ. A name of one place: Omagh. MacLysaght calls it 'quite numerous' there and a variant of MacCall, and the record agrees.
• McGinley · Mag Fhionnghaile · Gaelic sept
  Son of Fionnghal, ‘fair valour’. A well-known Donegal family, Woulfe writes, some of whom settled in Westmeath and Longford.
• McGoldrick · Mag Ualghairg · Gaelic sept
  Son of Ualgharg, ‘proud-fierce’. A branch of the O'Rourkes in Co. Leitrim and other parts of Connacht, Woulfe writes.
• McGonigle · Mag Congail · Gaelic sept
  A variant of Mac Congail; Woulfe gives no meaning here. A well-known Tirconnell surname, Woulfe writes. Donald MagCongail was Bishop of Raphoe from 1562 to 1589, and one of the few Irish bishops at the Council of Trent.
• McGovern · Mág Shamhradháin · Gaelic sept
  Son of Samhradhán, 'summer's child'. Mag Shamhradháin, son of Samhradhán, from samhradh, summer: an old Bréifne family whose head was chief of Teallach Eachach, the barony of Tullyhaw in north-west Cavan. Woulfe notes they are still very numerous.
• McGrath · Mac Craith · Gaelic learned family
  Son of Mac Raith, 'son of grace'. Mac Raith, son of grace or prosperity, an old Irish personal name; written Mac Craith, Mag Raith and Magrath by turns. Three families: a Donegal family whose head was coarb of St Daveog at Lough Derg and lived at the castle of Termon Magrath near Pettigo; a Thomond family who were hereditary poets and chroniclers to the O'Briens; and a Scottish family from Kintail, some of whom settled in the north.
• McGuinness · Mag Aonghusa · Gaelic dynasty
  Son of Aonghus. Mag Aonghusa, son of Aonghus, one choice: an ancient and powerful family in Down. They were first lords of Clann Aodha, but in the 12th century their power grew until they became lords of all Uí Eachach, the baronies of Upper and Lower Iveagh, and the annals name many of their chiefs.
• McInerney · Mac an Airchinnigh · Gaelic learned family
  Son of the erenagh — the hereditary steward of church lands. Mac an Airchinnigh, son of the erenagh, the steward of church lands. Woulfe describes several separate families, each an offshoot of an erenagh family: a Roscommon family, erenaghs of St Patrick's church at Elphin; and a Thomond family, numerous in Clare and Limerick, who held land in the parish of Ballysally until the Cromwellian confiscations.
• McIntyre · Mac an tSaoir · Gaelic sept & Scots (Clan MacIntyre)
  Son of the craftsman, from saor, ‘a mason or carpenter’. ‘Son of the craftsman’. Woulfe says there were no doubt several distinct families of the name.
• McKenna · Mac Cionaoith · Gaelic sept
  Son of Cionaoth. Mac Cionaodha, son of Cionaodh. The family belonged to the southern Uí Néill but were chiefs of the barony of Truagh in north Monaghan; a separate family in Roscommon followed the O'Connors.
• McKeown · Mac Eoin · Norman-Gaelic
  Son of Eoin or Eoghan — John, or the older Irish Eoghan. The Mac Eoin Bissetts came to the Glens of Antrim in the thirteenth century with John Bissett and became a Gaelic sept in all but ancestry — Normans of Scottish exile speaking Irish within a century.
• McLoughlin · Mac Lochlainn · Gaelic dynasty
  Son of Lochlann, 'the Norse-lander'. Lochlainn is a name of Norse origin. The Mac Lochlainns were the senior branch of the northern Uí Néill and, before the 13th century, the most powerful family in Ulster; they were seated in Inishowen, where the name is still common.
• McMahon · Mac Mathghamhna · Gaelic dynasty
  Son of Mathghamhain, 'bear'. Mathghamhain means bear, and there are two great families. The MacMahons of Thomond, a branch of the O'Briens, descend from Mahon, son of Murtagh Mór O'Brien, King of Ireland 1094–1119; they held Corca Bhaiscinn, the baronies of Moyarta and Clonderlaw in south-west Clare, and Marshal MacMahon, President of France, was of this family.
• McManus · Mac Mághnais · Gaelic sept
  Son of Magnus — from Latin magnus, 'great'. Maghnus is the Latin Magnus, a name the Norse took up in honour of Charlemagne, Carolus Magnus, and brought to Ireland. Woulfe gives two families: a Roscommon family descended from Maghnus, son of Turlough Mór O'Connor, King of Ireland, killed in 1181; and a Fermanagh family descended from Maghnus, son of Donn Maguire, chief of Fermanagh, who died in 1302, whose head lived on Belle Isle in Lough Erne.
• McNally · Mac Con Allaidh · Gaelic sept
  Son of Cú Allaidh, 'the wild hound' — the wolf. Mac an Fhailghigh, son of the poor man, compared by Woulfe with de Paor, Power: a Mayo surname borne by a family of Welsh or Norman origin, and common in the 16th century in parts of Ulster and Leinster. In the north, he warns, it is easily confused with Mac Con Uladh, MacAnulla.
• McNelis · Mac Niallghuis · Gaelic sept
  Son of Niallghus, 'champion-choice'. A Donegal surname: Woulfe gives Mac Niallghuis, 'son of Niallghus' (champion-choice), the name of a West Ulster family, some of whom have settled in Mayo. The name reached us from a reader whose people are from Ardara.
• McNulty · Mac an Ultaigh · Gaelic sept
  Son of the Ulsterman. Held to be a branch of the MacDonlevys, the ruling family of the Ulaid, who fled west after the Normans took their kingdom in 1177 — and whose descendants were named for where they came from.
• McVeigh · Mac an Bheatha · Gaelic sept
  Son of Mac an Bheathadh, a personal name meaning ‘son of life’. A common surname in many parts of Ulster, Woulfe writes, also found in parts of Leinster and Connacht. Its English forms were often made to match those of Mac Fhíodhbhuidhe, so many of the family appear as MacAvoy or MacEvoy.
• Meehan · Ó Miadhacháin · Gaelic sept
  Descendant of Miadhachán, 'the honourable'. Miadhachán is from miadhach, honourable. Woulfe calls Ó Miadhacháin a common surname in nearly every part of Ireland, and thinks there were no doubt several distinct families of it; he records Meehan, Meighan, Mehan and many other spellings.
• Merrigan · Ó Muireagáin · Gaelic sept
  Descendant of Muireagán, a diminutive of a name beginning Muir-. One of the chief families of Teffia, in what are now Westmeath and Longford, and sometimes lords of the whole district. Woulfe says they vanish from history around the beginning of the 12th century and seem to have scattered across Ireland.
• Minogue · Ó Muineog · Gaelic sept
  Descendant of Muineog — a diminutive of manach, 'monk'. Woulfe gives the root as a diminutive of manach, a monk, and records the name as common in Clare and Offaly. It is old enough in the record to have produced a bishop: Cléirchen Ó Muineóg held the see of Leighlin in the 11th century.
• Mitchell · Mistéil · Norse-Scots
  From Michael. Mistéil, son of Michell, a form of Michael. In Ulster most Mitchells are of Scottish or English settler descent.
• Molloy · Ó Maolmhuaidh · Gaelic sept
  Descendant of Maolmhuadh, 'noble chief'. Maolmuadh means noble chief. The O'Molloys were a distinguished family of the southern Uí Néill, of the same descent as the Mageoghegans; both were once a single clan, Cinéal Fiachach, from Fiacha, son of Niall of the Nine Hostages.
• Moloney · Ó Maoldhomhnaigh · Gaelic sept
  Descendant of Maoldomhnaigh, 'devoted to Sunday, or to the Church'. A Dalcassian family, Woulfe writes, chiefs of a district in the barony of Tulla, Co. Clare, and very numerous throughout Munster.
• Monaghan · Ó Manacháin · Gaelic sept
  Descendant of Manachán, 'little monk'. Woulfe derives the family from Manachán, a warrior noted by the Four Masters at 866. They were chiefs of Uí Briúin na Sionna in the barony of Ballintober, Roscommon, until 1249, when the O'Beirnes ousted them.
• Mooney · Ó Maonaigh · Gaelic sept
  Descendant of Maonach. Woulfe records three separate families: chiefs of Clann Murthuile in Roscommon, a branch of the Uí Fiachrach on the south shore of Sligo Bay in the barony of Tireragh, and a branch of the Siol nAnmchadha in south-east Galway. By the end of the 16th century the name was found in every part of Ireland.
• Moore · Ó Mórdha · Gaelic sept
  Descendant of Mórdha, 'majestic'. Mórdha means majestic. The O'Mores were chiefs of Laois, with their chief fortress at Dunamase near Portlaoise, whose ruins still stand, and Woulfe says they defied the whole power of the English invaders for several centuries.
• Moran · Ó Móráin · Gaelic sept
  Descendant of Mórán, 'the great one'. Mórán is a pet form of mór, great. The Ó Móráin were a branch of the Uí Fiachrach in Mayo and Sligo who ruled a wide district on both sides of the Moy, with the chief at Ardnaree near Ballina, and Woulfe calls them a highly respectable family.
• Moriarty · Ó Muircheartaigh · Gaelic sept
  Descendant of Muircheartach, 'skilled navigator' — from muir, the sea. Muircheartach is a sea-director, an expert navigator, and it is one of the very few Irish surnames with the sea in its meaning. Woulfe places the Kerry family as chiefs of Aos Aisde, a district he reckons lay along the river Maine, which is the country behind Castlemaine and the Dingle peninsula.
• Moroney · Ó Maolruanaidh · Gaelic septs (several)
  Descendant of Maolruanaidh, ‘follower of Ruanaidh’. Woulfe names four families. One was a Fermanagh family who were lords of that county before the Maguires.
• Morrison · Mac Muiris / Ó Muirgheasáin · Ulster Scots / Gaelic
  Son of Maurice / descendant of Muirgheasán. In Donegal, Morrison can be Ó Muirgheasáin, a diminutive of Muirgheas, an old Donegal surname, pronounced Ó Bríosáin and also anglicised Bryson, and in Mayo Price. Many Ulster Morrisons are of Scottish descent, a separate origin.
• Morrissey · Ó Muirgheasa · Gaelic sept
  Descendant of Muirgheas, 'sea-choice'. Woulfe makes Ó Muirgheasa a branch of the Uí Fiachrach, formerly chiefs of a district on the southern shore of Sligo Bay, in the barony of Tireragh. He thought there were probably several other distinct families of the name, which was common in most parts of Ireland.
• Moynihan · Ó Muimhneacháin · Gaelic sept
  Descendant of the Munsterman. Muimhneachán is, literally, the Munsterman — which makes the name a puzzle, since you would hardly be called that at home. Woulfe answers it: there are two families, and the older is a Uí Fiachrach family in Erris in Mayo, where a Munsterman would indeed be worth naming, and where the surname is sometimes translated outright as Munster.
• Mulcahy · Ó Maolchathaigh · Gaelic sept
  Descendant of the devotee of St Cathach ('battle'). Ó Maolchatha, battle-chief, or follower of Cathach. Woulfe calls it a well-known Munster surname that seems to have begun in south Tipperary and is now also common in Waterford, Cork and Limerick.
• Muldoon · Ó Maoldúin · Gaelic septs (several)
  Descendant of Maoldúin, ‘chief of the fort’. Several distinct families bore the name, Woulfe says. One was an Oirghialla family who were chiefs of Feara Luirg, now the barony of Lurg in north Fermanagh, until the end of the 14th century, and who were still numerous in that county.
• Mulgrew · Ó Maolchraoibhe · Gaelic sept
  Descendant of Maolchraoibhe, 'chief of Craobh'. An Oriel family, Woulfe writes, first west of the Upper Bann, who later moved into Clannaboy as followers of the O'Neills. At the start of the 17th century they held the west side of Knockbreda near Belfast, though the name was already scattered through Tyrone, Armagh and Antrim.
• Mulhall · Ó Maolchathail · Gaelic sept
  Descendant of Maolchathail, ‘servant of St Cathal’. An old family in Offaly and Laois, Woulfe writes, still numerous in Laois and in other parts of Leinster.
• Mulhern · Ó Maoilchiaráin · Gaelic sept
  Descendant of the servant of St Ciarán. An ecclesiastical family, Woulfe writes, erenaghs of Eaglais Beag at Clonmacnoise and of Ardcarne in Roscommon. A branch settled in Donegal before the end of the 16th century, when the name was most frequent in Westmeath, Roscommon and Donegal.
• Mulholland · Ó Maolchalann · Gaelic sept
  Descendant of Maolchalann, 'chief of the calends'. Keepers of the Bell of St Patrick, the Bell of the Testament, from at least the twelfth century to the end of the eighteenth, seated in the barony of Loughinsholin in Derry with a branch early settled in Antrim. Woulfe records two other families of the name, in Limerick and Meath, and reckons the Ulster line the only one still extant.
• Mullally · Ó Maolalaidh · Gaelic sept
  Descendant of Maolaladh, 'speckled chief'. A branch of the Uí Maine, Woulfe writes, once one clan with the O'Naghtens, holding the plain around Loughrea until the Burkes pushed them out about the time of the Anglo-Norman invasion. They settled at Tullaghnadaly, Tolendal, four miles north of Tuam.
• Mullan · Ó Maoláin · Gaelic sept
  Descendant of Maolán, 'the tonsured one'. From Maolán, a diminutive of maol, bald — and in Irish names that baldness is usually the tonsure of a monk or a devotee rather than a hairline. Woulfe calls it one of the commonest surnames in the country, found in almost every part of it and under a great spread of anglicised forms: Mullan, Mullen, Mullane, Millane, Moylan, Mullins, Mollan.
• Mullaney · Ó Maoileanaigh · Gaelic sept
  Descendant of Maolsheanaigh, ‘servant of St Seanach’. A common surname in Connacht, Woulfe writes, especially in Roscommon, where in 1540 the family was seated near Loch Cé, and in Mayo and Sligo. It was also found in Cork and Antrim.
• Mullarkey · Ó Maoilearca · Gaelic sept
  Descendant of the servant of St Earc. Formerly a Tír Chonaill surname, Woulfe writes, and by his time more common in Connacht.
• Mulligan · Ó Maolagáin · Gaelic sept
  Descendant of Maolagán, 'the little tonsured one'. Maolagán is a pet form of maol, bald. The Ó Maolagáin were a Tír Chonaill family, chiefs of Tír Mac Carthainn in the east of the barony of Boylagh in Donegal, dispossessed and dispersed early, and the Plantation scattered them further into Mayo and Monaghan.
• Mulqueen · Ó Maolchaoin · Gaelic sept
  Descendant of Maolcaoin, 'gentle chief'. A bardic family of Thomond. Woulfe cites the Four Masters at 1096 for the death of Ua Maelcain, ollamh of the Dál gCais, and names O'Mulqueen of Ballymulqueeny among the besiegers of Ballyally castle in 1641.
• Mulvey · Ó Maoilmhiadhaigh · Gaelic sept
  Descendant of Maolmiadhach, 'honourable chief'. Of the same stock as the MacRannals and O'Farrells, Woulfe writes, chiefs of Muinntear Chearbhalláin in Magh Nisi on the east side of the Shannon in Co. Leitrim, and sometimes of all Muinntear Eolais.
• Mulvihill · Ó Maoilmhichil · Gaelic sept
  Descendant of the servant of St Michael. A family of Síol Muireadhaigh in Roscommon, Woulfe writes, descended from Maolmhichil, a chief who fought at Cill Ua nDaighre near Dublin in 866. Once chiefs of Corca Sheachlainn in east Roscommon, they lost that rank early.
• Murphy · Ó Murchadha · Gaelic sept
  Descendant of Murchadh, 'sea-warrior'. Murchadh means sea-warrior, and Ó Murchadha is Ireland's most numerous surname because several separate families took it. Woulfe names three: a Cinéal Eoghain family who were chiefs of Síol Aodha in Tyrone; a Uí Fiachrach family on the southern shore of Sligo Bay, in the parishes of Skreen and Templeboy, dispossessed in the 13th century; and a branch of the Uí Ceinnsealaigh who were chiefs of Uí Feilme, the barony of Ballaghkeen in east Wexford, and stayed a distinct clan into the early 17th century.
• Murray · Ó Muireadhaigh / Mac Muireadhaigh · Gaelic sept & Scots
  Descendant of Muireadhach, 'seafarer / lord'. Muireadhach means a seaman or mariner, and also a lord. Woulfe describes Ó Muireadhaigh as the name of several distinct families: the O'Murrys of Mayo, Roscommon, Westmeath and Cork were ruling families who once held wide districts, but all had long been dispossessed and scattered by his time.
• Murtagh · Mac Muircheartaigh · Gaelic sept
  Son of Muircheartach, 'sea-director, navigator'. Woulfe calls Mac Muircheartaigh a very common Irish patronymic that in many places hardened into a family name, so many unrelated Murtaghs share it; a Scottish family of the name in Argyll also sent members to Ulster. He names no homeland; the counties shown are approximate.

Also spelled with M

These are listed on the atlas under another spelling, but the M form is the one many families carry.