View source for O'Reilly

{{About|the surname}}
{{EngvarB|date=August 2025}}
{{Use dmy dates|date=August 2025}}
{{Royal house
| surname =  O'Reilly<br>''Ó Raghallaigh''
| coat of arms = [[File:Coat of arms of O'Reilly.svg|150px|O'Reilly arms]]
| country = [[Connacht|Kingdom of Connacht]]
| parent house = [[Uí Briúin]] Bréifne
| titles = 
* King of [[East Bréifne]]
* King of Muintir Maelmórdha
* Conde de O'Reilly
| founder = Ragheallach mac Cathalan
| final ruler = [[Maelmordha O'Reilly]]
| founding year =
| dissolution = 1602
| cadet branches = Brady<br>Vesey
}}
[[File:Cavan crest.svg|thumb|upright=0.5|A [[Defacement (flag)|defaced]] O'Reilly crest adorns the coat of arms of [[County Cavan]], their historic patrimony]]

'''O'Reilly''' ({{langx|ga|'''Ó Raghallaigh'''}})<ref>{{Cite web |title=Raghallach — Database of Irish-language Surnames |url=https://www.gaois.ie/ga/surnames/10622/ |access-date=26 December 2022 |website=Gaois}}</ref> is a common [[Irish surname]]. The O'Reillys were historically the kings of [[East Bréifne]] in what is today [[County Cavan]]. The clan were part of the [[Connachta]]'s [[Uí Briúin]] Bréifne kindred and were closely related to the [[Ó Ruairc]] (O'Rourkes) of [[West Bréifne]].{{Citation needed|date=August 2025}} O'Reilly is ranked tenth in the [[List of most common surnames in Europe#Republic of Ireland|top twenty]] list of most common Irish surnames. It is also the [[patronymic]] form of the Irish name [[Reilly (surname)|Reilly]] ({{langx|ga|Raghallach}}).<ref>{{Cite web |title=Ó Raghailligh - Irish Names and Surnames |url=https://www.libraryireland.com/names/or/o-raghailligh.php |website=LibraryIreland.com |access-date=26 December 2022 }}</ref>

==Naming conventions==
{{Main|Irish personal naming system}}

{| class="wikitable" style="text-align:right"
|-
! width=20% | Male
! width=20% | Daughter
! width=20% | Wife ''<small>(Long)</small>''
! width=20% | Wife ''<small>(Short)</small>''
|-
| align="center"| Ó Raghallaigh<ref>{{cite news|url=http://www.sloinne.ie/surname/ga/o-raghallaigh/|publisher=Sloinne|title=Ó Raghallaigh |date=5 December 2015}}</ref>
| align="center"| Ní Raghallaigh
| align="center"| Bean Uí Raghallaigh
| align="center"| Uí Raghallaigh
|}

==Overview==
Usually anglicised as [[Reilly (surname)|Reilly]], O'Reilly or Riley, the original form of the name, Ó Raghallaigh, denotes "descendant of Raghallach".

The Ó Raghallaigh family were part of the [[Connachta]], with the [[:wikt:eponym|eponymous]] Raghallach said to have died at the [[Battle of Clontarf]] in 1014.{{Citation needed|date=August 2025}}

The name is common and widespread throughout Ireland, ranked 11th most common in 1890<ref>Matheson, Robert E. (1894), ''Special report on surnames in Ireland, with notes as to numerical strength, derivation, ethnology, and distribution; based on information extracted from the indexes of the General register office. Appendix to the Twenty-Ninth Detailed Annual Report of the Registrar-General of Marriages, Births, and Deaths in Ireland'', Dublin: For Her Majesty's Stationery Office by Alexander Thom & Co. (Limited), p. 9 ([https://archive.org/details/cu31924029805540/page/n11 accessible online])</ref> and in 1997.<ref>Murphy, Sean J. (2014), A Survey of Irish Surnames 1992–97. In: ''Studies in Irish Genealogy and Heraldry'', Windgates, County Wicklow, pp. 14–29 (first published 2008, last revision 2014), here p. 27 ([https://www.academia.edu/9204227/A_Survey_of_Irish_Surnames_1992-97 accessible online])</ref>

A self-proclaimed and disputed O'Reilly Clan Chieftain to this day is at odds with the O'Rourke Clan Chieftain because he contests the recognised O'Rourke claim on the title Prince of Breifne.<ref>[[Stefan Michael Newerkla|Newerkla, Stefan Michael]] (2020), Das irische Geschlecht O'Reilly und seine Verbindungen zu Österreich und Russland [The Irish O'Reilly family and their connections to Austria and Russia]. In: ''Diachronie – Ethnos – Tradition: Studien zur slawischen Sprachgeschichte [Diachrony – Ethnos – Tradition: Studies in Slavic Language History].'' Eds. Jasmina Grković-Major, Natalia B. Korina, [[Stefan Michael Newerkla|Stefan M. Newerkla]], Fedor B. Poljakov, Svetlana M. Tolstaja. Brno, Tribun EU, pp. 259–279, here 263–265 [https://uscholar.univie.ac.at/o:1405256 (accessible online).]</ref> This was settled in 1994 when the Chief Herald of Ireland made the O'Rourke Chief the Prince of [[Breifne]], but the Office of the Chief Herald stopped granting courtesy titles to Gaelic Chiefs in 2003 (see [[O'Rourke]]).

==People with the surname==
<!--Only list people notable enough to have an article.-->

===O'Reilly===
People with the surname O'Reilly include:<ref>{{cite journal |author-link=Stefan Michael Newerkla |last=Newerkla |first=Stefan Michael |date=2020 |title=Das irische Geschlecht O'Reilly und seine Verbindungen zu Österreich und Russland |trans-title=The Irish O'Reilly family and their connections to Austria and Russia |journal=Diachronie – Ethnos – Tradition: Studien zur slawischen Sprachgeschichte |trans-journal=Diachrony – Ethnos – Tradition: Studies in Slavic Language History |editor1-first=Jasmina |editor1-last=Grković-Major |editor2-first=Natalia B. |editor2-last=Korina |editor3-first=Fedor B. |editor3-last=Poljakov |editor4-first=Svetlana M. |editor4-last=Tolstaja |location=Brno, Tribun EU |pages=259–279 |url=https://uscholar.univie.ac.at/o:1405256 }}</ref><ref>{{cite web |url=http://www.irishsurnames.com/cgi-bin/gallery.pl?name=oreilly&capname=O'Reilly&letter=r&user=IIS&refer=ISP&item=ss |title=O'Reilly coat of arms, family crest and O'Reilly family history |website=IrishSurnames.com |access-date=1 January 2008 }}</ref>
* [[Alejandro O'Reilly]] (1722–1794), second Spanish governor of colonial Louisiana
* [[Andreas O'Reilly von Ballinlough|Andreas O'Reilly]] (1742–1832), Irish-born Austrian general
* [[Bernard O'Reilly (author)|Bernard O'Reilly]] (1903–1975), Australian author, found the wreck of a Stinson aircraft in the McPherson Range, 1937
* [[Bernard O'Reilly (bishop of Hartford)]] (1803–1856), Irish Roman Catholic bishop
* [[Bernard O'Reilly (bishop of Liverpool)]] (1824–1894), Irish Roman Catholic bishop
* [[Bill O'Reilly (political commentator)|Bill O'Reilly]] (born 1949), American commentator and television show host of [[The O'Reilly Factor]] on the Fox News Channel
* [[Bill O'Reilly (cricketer)|Bill O'Reilly]], Australian cricketer
* [[Bob O'Reilly]], Australian rugby league footballer
* [[Caitriona O'Reilly]], Irish poet and critic
* [[Cal O'Reilly]], Canadian ice hockey player
* [[Cameron O'Reilly]], Irish and Australian businessman
* [[Cassia O'Reilly]], Irish singer-songwriter
* [[Charles O'Reilly]] (died 1800), Roman Catholic Bishop of Kilmore from 1798 to 1800
* [[Danny O'Reilly]], lead singer of Irish band, The Coronas
* [[David O'Reilly (disambiguation)|David O'Reilly]], several people
* [[Dermot O'Reilly]] (1942–2007), Irish-born Canadian singer and songwriter in band Ryan's Fancy, working in Newfoundland and Labrador
* [[Des O'Reilly]] (1954–2016), Australian rugby league player
* [[Emily O'Reilly]], Irish journalist
* [[Emma O'Reilly]], Irish physiotherapist and cycling soigneur who worked for Lance Armstrong
* [[Eugenia O'Reilly-Regueiro]], Mexican mathematician
* [[Finbarr O'Reilly]], Canadian photographer
* [[Gary O'Reilly]], English footballer
* [[Genevieve O'Reilly]], Irish actress
* [[Heather O'Reilly]] (born 1985), American soccer player
* [[Hugh Reily]] (1630–1695), Irish M.P. and political author
* [[James Reilly (Canadian politician)]] (1835–1909), Canadian businessman and politician from Alberta
* [[James O'Reilly (priest)|James O'Reilly]], American Roman Catholic priest
* [[Jennifer O'Reilly]] (1943–2016), medieval historian of Britain and Ireland
* [[Joe O'Reilly]], Irish politician
* [[John Reyly]] (recte O'Reilly) (c. 1646–1717), M.P. for Cavan County in the Parliament of Ireland of 1689
* [[John B. O'Reilly Jr.]] (1948–2025), American politician from Michigan
* [[John O'Reilly (politician)|John O'Reilly]] (born 1940), Canadian politician from Ontario
* [[Kyle O'Reilly]] (born 1987), ring name of Canadian professional wrestler Kyle Greenwood
* [[Leonora O'Reilly]], American feminist
* [[Luke O'Reilly (disambiguation)]], several people
* [[Mary Margaret O'Reilly]], assistant director of the United States Bureau of the Mint from 1924 to 1938
* [[Matthew O'Reilly]], Irish politician and farmer 
* [[East Breifne|O'Reilly, Lords of Bréifne]] (c. 1161 – 1607), Irish rulers
* [[Patrick Thomas O'Reilly]] (1833–1892), US Catholic bishop, born in Ireland
* [[Peter O'Reilly (civil servant)]] (1827–1905), Irish-born settler and official in the Colony of British Columbia
* [[Peter O'Reilly (hurler)]] (1902–1940), Irish hurler
* [[Philip O'Reilly (Cavan County MP)]] (c. 1600–1655), M.P. for County Cavan 
* [[Philip Og O'Reilly]] (c. 1640 – 1703), M.P. for Cavan Borough in the Parliament of Ireland of 1689
* [[Philip Reyley]] (recte O'Reilly) (c. 1630 – after 1689), M.P. for Cavan County in the Parliament of Ireland of 1689
* [[Randall C. O'Reilly]] (born 1967), American professor of psychology, developer of [[Leabra]]
* [[Robert O'Reilly]] (born 1950), American actor
* [[Ruth O'Reilly]] (born 1981), Irish rugby union player
* [[Ryan O'Reilly (ice hockey)]] (born 1991), Canadian ice hockey player
* [[Ryan O'Reilly (wrestler)]] (born 1980), American professional wrestler
* [[Sam O'Reilly]] (born 2006), Canadian ice hockey player
* [[Samuel O'Reilly]] (1854–1909), American tattoo artist and inventor
* Stephen O'Reilly (born 1964) (better known as [[Stephen Egerton (guitarist)|Stephen Egerton]]), American musician
* [[Stephen O'Reilly (actor)|Stephen O'Reilly]], American actor
* [[Stephen O'Reilly (footballer)|Stephen O'Reilly]], Australian footballer
* [[Terry O'Reilly]], Canadian hockey player
* [[Tim O'Reilly]] (born 1954), Irish-American founder of O'Reilly Media
* [[Tom O'Reilly (Cavan politician)|Tom O'Reilly]] (1915–1995), Irish Gaelic footballer and politician
* [[Tom O'Reilly (Fermanagh politician)|Tom O'Reilly]], Irish Sinn Féin politician
* [[Tom O'Reilly (rugby league)|Tom O'Reilly]], Papua New Guinea international
* [[Tony O'Reilly]] (1936–2024), Irish businessman
* [[Valli O'Reilly]], American makeup artist
* [[Walter Cresswell O'Reilly]] (1877–1954), Australian Commonwealth Film Censor and founding President of the National Trust of Australia

===O'Riley===
* [[Bunny Wailer]] (1947–2021), Jamaican reggae musician sometimes known as Bunny O'Riley
* [[Christopher O'Riley]] (born 1956), American classical pianist and public radio show host
* [[Don O'Riley]] (1945–1997), American Major League Baseball pitcher
* [[Jon Riley]] (1824–1879), US army deserter also known as John O'Riley
* [[Matt O'Riley]] (born 2000), English footballer at Celtic F.C.

===Ní Raghallaigh===
* [[Shónagh Ní Raghallaigh]], Irish politician

===Riley===
{{Main|Riley (surname)}}

==Fictional characters with the surname==
* Mr. O'Reilly, portrayed by the Irish actor [[David Kelly (actor)|David Kelly]] in the ''[[Fawlty Towers]]'' episode "[[The Builders]]"
* Aloysius Umbongo N'Danga O'Reilly, in the song "Baguette Dilemma for the Booker Prize Guy" by the band [[Half Man Half Biscuit]] on their 2014 album ''[[Urge for Offal]]''
* Corporal Walter "Radar" O'Reilly, in the ''[[M*A*S*H]]'' media franchise

==See also==
{{Wiktionary|O'Reilly}}
* [[Riley (disambiguation)]]
* [[Ryley (name)]]
* [[Riley (surname)]]
* "[[Baba O'Riley]]", a song by The Who

==References==
{{Reflist}}

==External links==
{{Commons category|O'Reilly (surname)}}
*[http://oreillyreillyclan.blogspot.co.uk/ The O'Reilly Clan]
*[http://www.libraryireland.com/Pedigrees1/o-reilly-1-heremon.php O'Reilly family pedigree] at Library Ireland
*[http://genforum.genealogy.com/oreilly/messages/855.html Statistics about O'Reilly Ancestors]
*[http://www.araltas.com/features/reilly/ O'Reilly, Reilly, Riley. History of family]
*[http://www.irishtimes.com/ancestor/surname/index.cfm?fuseaction=History&Surname=Riley&UserID= Irish Times surname entry for "Riley"]
*[https://uscholar.univie.ac.at/o:1405256 The Irish O'Reilly family and their connections to Austria and Russia] by [[Stefan Michael Newerkla|Stefan M. Newerkla]]

{{Surname}}
{{Connachta}}
{{Gaels}}

{{DEFAULTSORT:Oreilly}}
[[Category:Anglicised Irish-language surnames]]
[[Category:English-language surnames]]
[[Category:Irish families]]
[[Category:Patronymic surnames]]
[[Category:Surnames of Irish origin]]