2000
#633
National surname rank
Recorded bearers 48,656
First available Census row
Per 100,000 18.04
Uncommon Last name
Oneill
A surname of Irish origin meaning "descendant of Niall," referring to Niall of the Nine Hostages, an Irish king.
According to the 2020 US Census Bureau surname tables, roughly 56,608 Americans carry the last name Oneill. That puts it at #673 in the national surname ranking, appearing at a frequency of 16.52 per 100,000 people (about 1 in 6,055 residents).
This page is the full Name Census profile for the Oneill 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 Oneill with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
57K
1 in 6,055
Census rank
#673
2020 decennial data
Per 100,000
16.5
Frequency rate
Recorded bearers
49K
uncommon in the US
Popularity narrative
The Census Bureau recorded 49,365 bearers of the surname Oneill in its 2020 decennial surname file. At a rate of 16.52 per 100,000 residents, it holds the 673rd position in the national surname ranking.
Among Census respondents with the surname Oneill, the largest self-reported group is White at 89.8%. The next largest groups are Hispanic (5.2%) and Two or More Races (2.8%).
Origin
Meaning and origin of Oneill
The surname O'Neill is of Irish origin, derived from the Gaelic "Ua Néill" meaning "descendant of Niall." It traces its roots back to the ancient kingdom of Ailech in the northern parts of Ireland, particularly in modern-day County Tyrone and County Londonderry.
The surname has its origins in the 4th century AD when Niall Noígiallach, also known as Niall of the Nine Hostages, was a prominent and powerful High King of Ireland. He established the Uí Néill dynasty, which ruled various parts of Ireland for centuries.
One of the earliest recorded references to the name can be found in the Annals of Ulster, a chronicle of medieval Irish history. The annals mention several members of the Uí Néill dynasty, including Áed Oirdnide mac Néill, who died in 819 AD.
Another notable early reference is the Book of Armagh, a 9th-century manuscript containing some of the oldest surviving examples of Old Irish writing. It mentions several individuals with the surname, such as Fergus O'Neill, who was the abbot of Armagh in the 8th century.
During the Middle Ages, the O'Neills were one of the most powerful and influential families in Ireland. They ruled the Kingdom of Ailech and later the Principality of Tír Eógain (Tyrone). Some notable individuals include Niall Glúndub (d. 919), a powerful king of Ailech, and Muircheartach O'Neill (d. 1166), who was the King of Ailech and Tír Eógain.
In the 16th century, the O'Neills played a significant role in the Tudor conquest of Ireland. Hugh O'Neill, Earl of Tyrone (c. 1550–1616), led a major rebellion against English rule, which became known as the Nine Years' War (1594–1603). Despite initial successes, the rebellion was eventually defeated.
Other notable individuals with the surname include Sir Phelim O'Neill (c. 1604–1653), who led the Irish Rebellion of 1641, and John O'Neill (1834–1904), an Irish-American artist and sculptor who designed several famous monuments in New York City.
Demographics
Ancestry and ethnicity for Oneill
Among Census respondents with the surname Oneill, the largest self-reported group is White at 89.8%. The next largest groups are Hispanic (5.2%) and Two or More Races (2.8%).
The bar chart below shows how Oneill 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 Oneill surname at the time of the 2020 Census, not any inherent property of the name itself.
- White89.8% · 44,348
- Hispanic or Latino5.2% · 2,568
- Two or more races2.8% · 1,363
- Black or African American1.1% · 520
- Asian and Pacific Islander0.9% · 453
- American Indian and Alaska Native0.2% · 113
Timeline
Historical Census data for Oneill
Oneill 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
#689
National surname rank
Recorded bearers 50,028
+1,372 bearers (+2.8%)
Per 100,000 16.96
Rank movement Down 56 places
2020
#673
National surname rank
Recorded bearers 49,365
-663 bearers (-1.3%)
Per 100,000 16.52
Rank movement Up 16 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #633 | 48,656 | 18.04 | First available Census row | First available Census row |
| 2010 | #689 | 50,028 | 16.96 | +1,372 bearers (+2.8%) | Down 56 places |
| 2020 | #673 | 49,365 | 16.52 | -663 bearers (-1.3%) | Up 16 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 Oneill 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 | #689 | #673 | 2.3% |
| Count | 50,028 | 49,365 | -1.3% |
| Per 100K | 16.96 | 16.52 | -2.6% |
Between the 2010 and 2020 Census, the number of Oneill bearers went from 50,028 to 49,365 (-1.3% change). The surname moved up 16 positions in the national ranking, going from #689 to #673.
Notable bearers
Famous people with the surname Oneill
FAQ
Oneill surname: questions and answers
How many people in the U.S. have the surname Oneill?
Name Census estimates that about 56,608 living Americans carry the surname Oneill. Using the current population baseline, that works out to roughly 1 in 6,055 residents.
How common is Oneill?
Oneill ranks #673 in the 2020 Census surname tables and is classified on this site as "Uncommon." The Census recorded the name at a frequency of 16.52 per 100,000 residents, which is about 17 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 49,365 people with the surname Oneill. That is different from the site's living-bearer estimate (56,608), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 16.52 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 16.52 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 17 of them to have the surname Oneill.
Has Oneill become more or less common over time?
Between 2010 and 2020, the surname Oneill went from 50,028 recorded bearers to 49,365. That is a decrease of 663 (-1.3%). In the national ranking it rose from #689 to #673.
What does the Census say about the background of Oneill?
Among Census respondents with the surname Oneill, the largest self-reported group is White at 89.8%. The next largest groups are Hispanic (5.2%) and Two or More Races (2.8%). 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 Oneill in the 2020 Census, accounting for 89.8% (44,348 people in the source table).
What is the full ancestry breakdown?
Oneill appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (89.8%), Hispanic (5.2%), Two or More Races (2.8%). 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 Oneill (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 Oneill mean?
A surname of Irish origin meaning "descendant of Niall," referring to Niall of the Nine Hostages, an Irish king. 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 Oneill (16.52 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 have the last name Oneill?
If you just want to know how many people have the surname Oneill, HowManyOfMe.org gives you the headline number in one glance.