2000
#149,328
National surname rank
Recorded bearers 101
First available Census row
Per 100,000 0.04
Very Rare Last name
Oreilley
An Anglicized form of an Irish surname derived from a nickname meaning "descendant of the red (haired) one".
According to the 2020 US Census Bureau surname tables, roughly 135 Americans carry the last name Oreilley. That puts it at #143,511 in the national surname ranking, appearing at a frequency of 0.04 per 100,000 people (about 1 in 2,538,921 residents).
This page is the full Name Census profile for the Oreilley surname. You will find the Census Bureau frequency data, a multi-census history view, an ancestry and ethnicity breakdown based on self-reported demographics, the name's meaning and origin where available, and answers to the most common questions people ask about this surname.
Bearers in the US
135
1 in 2,538,921
Census rank
#143,511
2020 decennial data
Per 100,000
0.0
Frequency rate
Recorded bearers
118
very rare in the US
Popularity narrative
The Census Bureau recorded 118 bearers of the surname Oreilley in its 2020 decennial surname file. At a rate of 0.04 per 100,000 residents, it holds the 143511th position in the national surname ranking.
Among Census respondents with the surname Oreilley, the largest self-reported group is White at 81.4%. The next largest groups are Hispanic (10.2%) and Two or More Races (3.4%).
Origin
Meaning and origin of Oreilley
The surname O'Reilley is of Irish origin, derived from the Gaelic name Ó Raghallaigh, which means "descendant of Raghallach." The name Raghallach is composed of two elements: "rath," meaning prosperity or fortune, and "gallach," meaning valor or bravery. The prefix "Ó" signifies a male descendant.
The O'Reilleys were a prominent clan in County Cavan, Ireland, tracing their ancestry back to the 10th century. They were a powerful and influential family, known for their strong ties to the O'Reilly clan and their role in Irish history.
The earliest recorded mention of the O'Reilly surname dates back to the 12th century, appearing in the Annals of the Four Masters, a chronicle of medieval Irish history. In these annals, the O'Reillys are mentioned as lords of East Breifne, a territory that encompassed parts of modern-day counties Cavan and Longford.
One notable figure in the O'Reilly family was Mulroney O'Reilly (c. 1330-1401), who served as Lord of East Breifne and played a significant role in the Irish resistance against Anglo-Norman invasion. Another prominent member was Maolmordha O'Reilly (c. 1520-1566), a renowned poet and scholar who wrote extensively in the Irish language.
The name O'Reilly has also been associated with various place names in Ireland, such as Ballynahorich (Baile na hOiridhe), which translates to "the town of the O'Reillys." Other variations of the surname include O'Reilly, O'Reyly, O'Raily, and O'Ralley.
Several notable individuals with the surname O'Reilley have made their mark throughout history. One such figure is John Boyle O'Reilly (1844-1890), an Irish-born poet, journalist, and novelist who played a prominent role in the Irish revolutionary movement. He was exiled to Australia for his involvement in the Fenian Brotherhood but later escaped and settled in Boston, where he became a renowned writer and editor.
Another notable figure is Mary O'Reilley (1870-1957), an Irish-American educator and social worker who founded the first settlement house in Minnesota. She was instrumental in promoting education and social services for immigrant communities.
John O'Reilly (1891-1976) was an Irish-American newspaper editor and journalist who served as the editor of the New York Herald Tribune for over two decades. He was also a prominent figure in the Irish-American community and played a role in promoting Irish culture and literature.
Stephen O'Reilly (1765-1824) was an Irish-born soldier and adventurer who fought in various conflicts, including the American Revolutionary War and the Irish Rebellion of 1798. He later settled in Mexico and played a significant role in the country's independence movement.
Miles O'Reilly (1892-1973) was an American lawyer and politician who served as the 10th Lieutenant Governor of New York from 1939 to 1942. He was also a prominent figure in the Democratic Party and played a crucial role in shaping political developments in New York.
Demographics
Ancestry and ethnicity for Oreilley
Among Census respondents with the surname Oreilley, the largest self-reported group is White at 81.4%. The next largest groups are Hispanic (10.2%) and Two or More Races (3.4%).
The bar chart below shows how Oreilley bearers described their own race and ethnicity on the 2020 Census form. The Census Bureau groups responses into six broad categories: White, Black or African American, Hispanic or Latino, Asian and Pacific Islander, American Indian and Alaska Native, and Two or More Races. When a category has too few respondents for a given surname, the Bureau suppresses the figure to protect individual privacy, which is why some names show fewer than six slices.
Percentages are shown for every Census year so the breakdown stays comparable over time. When the source file also includes raw headcounts, Name Census shows those alongside the percentages in the legend.
Keep in mind that these are self-reported numbers. A person's surname does not determine their race or ethnicity, and the distribution you see here reflects the specific population who happened to carry the Oreilley surname at the time of the 2020 Census, not any inherent property of the name itself.
- White81.4% · 96
- Hispanic or Latino10.2% · 12
- Two or more races3.4% · 4
- Asian and Pacific Islander2.5% · 3
- American Indian and Alaska Native1.7% · 2
- Black or African American0.8% · 1
Timeline
Historical Census data for Oreilley
Oreilley appears in 3 published Census surname files: 2000, 2010, 2020. The cards below show how the name's rank and bearer count changed across each release.
2010
#143,149
National surname rank
Recorded bearers 116
+15 bearers (+14.9%)
Per 100,000 0.04
Rank movement Up 6,179 places
2020
#143,511
National surname rank
Recorded bearers 118
+2 bearers (+1.7%)
Per 100,000 0.04
Rank movement Down 362 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #149,328 | 101 | 0.04 | First available Census row | First available Census row |
| 2010 | #143,149 | 116 | 0.04 | +15 bearers (+14.9%) | Up 6,179 places |
| 2020 | #143,511 | 118 | 0.04 | +2 bearers (+1.7%) | Down 362 places |
For 2020, the Census Bureau published race and Hispanic-origin columns as counts rather than percentages. Name Census converts those counts back into shares so the ancestry section stays comparable with the older surname files.
Year on year
2010 vs 2020 Census
How has the Oreilley surname changed between Census years? The chart shows bearer count side by side, and the table compares rank, count, and frequency.
Census year comparison
20102020
| Metric | 2010 | 2020 | Change |
|---|---|---|---|
| Rank | #143,149 | #143,511 | -0.3% |
| Count | 116 | 118 | 1.7% |
| Per 100K | 0.04 | 0.04 | -1.3% |
Between the 2010 and 2020 Census, the number of Oreilley bearers went from 116 to 118 (+1.7% change). The surname moved down 362 positions in the national ranking, going from #143,149 to #143,511.
FAQ
Oreilley surname: questions and answers
How many people in the U.S. have the surname Oreilley?
Name Census estimates that about 135 living Americans carry the surname Oreilley. Using the current population baseline, that works out to roughly 1 in 2,538,921 residents.
How common is Oreilley?
Oreilley ranks #143,511 in the 2020 Census surname tables and is classified on this site as "Very Rare." The Census recorded the name at a frequency of 0.04 per 100,000 residents, which is about 0 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 118 people with the surname Oreilley. That is different from the site's living-bearer estimate (135), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 0.04 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 0.04 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 0 of them to have the surname Oreilley.
Has Oreilley become more or less common over time?
Between 2010 and 2020, the surname Oreilley went from 116 recorded bearers to 118. That is an increase of 2 (+1.7%). In the national ranking it fell from #143,149 to #143,511.
What does the Census say about the background of Oreilley?
Among Census respondents with the surname Oreilley, the largest self-reported group is White at 81.4%. The next largest groups are Hispanic (10.2%) and Two or More Races (3.4%). These figures come from the 2020 Census Bureau surname tables, based on how respondents described their own race and ethnicity.
Which group reports this surname most often?
White is the largest self-reported group for the surname Oreilley in the 2020 Census, accounting for 81.4% (96 people in the source table).
What is the full ancestry breakdown?
Oreilley appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (81.4%), Hispanic (10.2%), Two or More Races (3.4%). For 2020, the source file also published raw headcounts for each group, which is why this page can show both percentages and counts in the ancestry section.
Is this page using the latest Census data?
Yes. This page is using the latest surname file currently loaded on Name Census, which is 2020. The historical section above also keeps any older Census surname entries we have for Oreilley (2000, 2010, 2020).
Does the Census include every surname?
No. The Census Bureau only publishes surnames that appeared at least 100 times in a given decennial Census. That means very rare surnames are excluded entirely, and a surname can appear in one Census release but disappear from a later one if it falls below the reporting threshold.
Why don't the ancestry percentages always add up to exactly 100%?
There are two main reasons: rounding and suppression. The Census Bureau rounds published values, and it may suppress very small cells to protect privacy. For 2020, the Bureau also published raw group counts rather than direct percentages, so Name Census converts those counts back into shares for comparability across census years.
What does Oreilley mean?
An Anglicized form of an Irish surname derived from a nickname meaning "descendant of the red (haired) one". The fuller origin note on this page goes into more detail.
Where does the surname data come from?
All surname statistics on Name Census are drawn from the US Census Bureau's decennial surname frequency tables. These files list every surname that appeared 100 or more times in the 2020 Census, along with a count, a per-100,000 rate, and a self-reported demographic breakdown. You can read the full explanation on our methodology page.
How does Name Census estimate living bearers?
For surnames, Name Census does not age cohorts the way it does for first names. Instead, it takes the Census Bureau's published frequency for Oreilley (0.04 per 100,000) and applies that rate to the current U.S. resident population to estimate how many living Americans have the surname today.
How common is the surname Oreilley?
See how many Americans have the surname Oreilley on HowManyOfMe.org, our sister site built around that single question.