2000
#1,145
National surname rank
Recorded bearers 28,020
First available Census row
Per 100,000 10.39
Uncommon Last name
Oneil
A surname of Irish origin meaning "descendant of Niall," an Irish name meaning "champion."
According to the 2020 US Census Bureau surname tables, roughly 32,174 Americans carry the last name Oneil. That puts it at #1,230 in the national surname ranking, appearing at a frequency of 9.39 per 100,000 people (about 1 in 10,653 residents).
This page is the full Name Census profile for the Oneil 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.
For British records, Name Census UK has a British surname profile for Oneil with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
32K
1 in 10,653
Census rank
#1,230
2020 decennial data
Per 100,000
9.4
Frequency rate
Recorded bearers
28K
uncommon in the US
Popularity narrative
The Census Bureau recorded 28,057 bearers of the surname Oneil in its 2020 decennial surname file. At a rate of 9.39 per 100,000 residents, it holds the 1230th position in the national surname ranking.
Among Census respondents with the surname Oneil, the largest self-reported group is White at 85.5%. The next largest groups are Black (6.2%) and Hispanic (3.7%).
Origin
Meaning and origin of Oneil
The surname ONEIL is of Irish origin, deriving from the Gaelic Ó Néill, meaning "descendant of Neill." It originated in the 5th century AD with the Cenél nEógain clan, one of the two main branches of the Northern Uí Néill dynasty that dominated parts of Ireland until the 17th century.
The name traces its roots to Niall Noígiallach (Niall of the Nine Hostages), a legendary High King of Ireland who ruled in the late 4th and early 5th centuries. He is said to have taken hostages from rival kingdoms, leading to his epithet "of the Nine Hostages."
The ONEIL surname first appeared in written records in the Annals of Ulster, a chronicle of medieval Irish history. In the year 1022, the death of Flaithbhertach Ua Néill, King of Ailech, is recorded.
One of the earliest known bearers of the name was Muircheartach Ua Néill (1050-1166), a King of Ailech and Cenél nEógain who fought against the Norman invasion of Ireland in the 12th century.
The name is also found in the Domesday Book of 1086, a survey of landholdings in England commissioned by William the Conqueror. This suggests that some ONEILs may have migrated to England in the aftermath of the Norman conquest of Ireland.
A notable figure in Irish history was Hugh O'Neill (1550-1616), Earl of Tyrone, who led the Irish rebellion against English rule in the Nine Years' War (1594-1603). He was ultimately forced into exile in Rome after his defeat.
Another prominent ONEIL was John O'Neill (1786-1838), a United Irishman and revolutionary who took part in the Irish Rebellion of 1798 against British rule. He later fled to the United States and became a prominent figure in the Irish American community.
Other notable individuals with the surname ONEIL include Eugene O'Neill (1888-1953), the American playwright and Nobel laureate known for works such as "Long Day's Journey Into Night" and "The Iceman Cometh," and Shaquille O'Neal (born 1972), the former NBA superstar and one of the most dominant players in basketball history.
Demographics
Ancestry and ethnicity for Oneil
Among Census respondents with the surname Oneil, the largest self-reported group is White at 85.5%. The next largest groups are Black (6.2%) and Hispanic (3.7%).
The bar chart below shows how Oneil 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 Oneil surname at the time of the 2020 Census, not any inherent property of the name itself.
- White85.5% · 23,977
- Black or African American6.2% · 1,739
- Hispanic or Latino3.7% · 1,037
- Two or more races3.5% · 983
- Asian and Pacific Islander0.8% · 219
- American Indian and Alaska Native0.4% · 102
Timeline
Historical Census data for Oneil
Oneil 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
#1,220
National surname rank
Recorded bearers 28,949
+929 bearers (+3.3%)
Per 100,000 9.81
Rank movement Down 75 places
2020
#1,230
National surname rank
Recorded bearers 28,057
-892 bearers (-3.1%)
Per 100,000 9.39
Rank movement Down 10 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #1,145 | 28,020 | 10.39 | First available Census row | First available Census row |
| 2010 | #1,220 | 28,949 | 9.81 | +929 bearers (+3.3%) | Down 75 places |
| 2020 | #1,230 | 28,057 | 9.39 | -892 bearers (-3.1%) | Down 10 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 Oneil 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 | #1,220 | #1,230 | -0.8% |
| Count | 28,949 | 28,057 | -3.1% |
| Per 100K | 9.81 | 9.39 | -4.3% |
Between the 2010 and 2020 Census, the number of Oneil bearers went from 28,949 to 28,057 (-3.1% change). The surname moved down 10 positions in the national ranking, going from #1,220 to #1,230.
Notable bearers
Famous people with the surname Oneil
FAQ
Oneil surname: questions and answers
How many people in the U.S. have the surname Oneil?
Name Census estimates that about 32,174 living Americans carry the surname Oneil. Using the current population baseline, that works out to roughly 1 in 10,653 residents.
How common is Oneil?
Oneil ranks #1,230 in the 2020 Census surname tables and is classified on this site as "Uncommon." The Census recorded the name at a frequency of 9.39 per 100,000 residents, which is about 9 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 28,057 people with the surname Oneil. That is different from the site's living-bearer estimate (32,174), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 9.39 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 9.39 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 9 of them to have the surname Oneil.
Has Oneil become more or less common over time?
Between 2010 and 2020, the surname Oneil went from 28,949 recorded bearers to 28,057. That is a decrease of 892 (-3.1%). In the national ranking it fell from #1,220 to #1,230.
What does the Census say about the background of Oneil?
Among Census respondents with the surname Oneil, the largest self-reported group is White at 85.5%. The next largest groups are Black (6.2%) and Hispanic (3.7%). 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 Oneil in the 2020 Census, accounting for 85.5% (23,977 people in the source table).
What is the full ancestry breakdown?
Oneil appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (85.5%), Black (6.2%), Hispanic (3.7%). 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 Oneil (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 Oneil mean?
A surname of Irish origin meaning "descendant of Niall," an Irish name meaning "champion." 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 Oneil (9.39 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 many people are called Oneil?
See how common the surname Oneil is on HowManyOfMe.org, our sister site built around that single question.