2000
#12,437
National surname rank
Recorded bearers 2,289
First available Census row
Per 100,000 0.85
Rare Last name
Kilroy
An Irish surname derived from the Gaelic "Mac Giolla Rua," meaning "son of the red-haired servant."
According to the 2020 US Census Bureau surname tables, roughly 2,655 Americans carry the last name Kilroy. That puts it at #12,731 in the national surname ranking, appearing at a frequency of 0.77 per 100,000 people (about 1 in 129,098 residents).
This page is the full Name Census profile for the Kilroy 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 Kilroy with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
2.7K
1 in 129,098
Census rank
#12,731
2020 decennial data
Per 100,000
0.8
Frequency rate
Recorded bearers
2.3K
rare in the US
Popularity narrative
The Census Bureau recorded 2,315 bearers of the surname Kilroy in its 2020 decennial surname file. At a rate of 0.77 per 100,000 residents, it holds the 12731st position in the national surname ranking.
Among Census respondents with the surname Kilroy, the largest self-reported group is White at 93.0%. The next largest groups are Hispanic (3.1%) and Two or More Races (2.2%).
Origin
Meaning and origin of Kilroy
The surname Kilroy is believed to have originated in Ireland, specifically in the province of Munster. It is derived from the Irish Gaelic words "cill" meaning church and "ruaidh" meaning red or ruddy. This suggests that the name may have initially referred to someone who lived near a red or ruddy-colored church.
The earliest recorded instances of the name Kilroy can be traced back to the 12th century, when it appeared in various Irish annals and manuscripts. It was often spelled as "Ó Cillruaidh" or "Ó Cillruaidhe," which translates to "descendant of Cillruaidh."
In the 14th century, the name Kilroy was mentioned in the Annals of Inisfallen, a chronicle of medieval Irish history. This reference was in connection with a prominent family from County Cork, known as the Kilroy clan.
One of the earliest documented individuals with the surname Kilroy was John Kilroy, born around 1520 in County Tipperary. He was a notable landowner and chieftain of his clan during the 16th century.
Another historical figure bearing the name was Donogh Kilroy, who lived in County Limerick during the late 16th and early 17th centuries. He was a prominent member of the Irish gentry and played a role in the Desmond Rebellions against English rule.
In the 18th century, a notable Kilroy was James Kilroy, born in 1745 in County Cork. He was a renowned scholar and poet who wrote extensively in the Irish language.
During the 19th century, the name Kilroy gained recognition through the accomplishments of Michael Kilroy, born in 1818 in County Tipperary. He was a successful businessman and philanthropist who made significant contributions to the local community.
Another notable figure from the 19th century was Patrick Kilroy, born in 1832 in County Clare. He was a prominent politician and served as a member of the British Parliament, representing Irish constituencies.
While the name Kilroy has its roots in Ireland, it has since spread to other parts of the world due to Irish immigration. Over the centuries, various branches of the Kilroy family have established themselves in countries such as the United States, Canada, Australia, and New Zealand.
Demographics
Ancestry and ethnicity for Kilroy
Among Census respondents with the surname Kilroy, the largest self-reported group is White at 93.0%. The next largest groups are Hispanic (3.1%) and Two or More Races (2.2%).
The bar chart below shows how Kilroy 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 Kilroy surname at the time of the 2020 Census, not any inherent property of the name itself.
- White93.0% · 2,153
- Hispanic or Latino3.1% · 72
- Two or more races2.2% · 52
- Asian and Pacific Islander1.0% · 24
- Black or African American0.5% · 12
- American Indian and Alaska Native0.1% · 2
Timeline
Historical Census data for Kilroy
Kilroy 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
#12,953
National surname rank
Recorded bearers 2,371
+82 bearers (+3.6%)
Per 100,000 0.80
Rank movement Down 516 places
2020
#12,731
National surname rank
Recorded bearers 2,315
-56 bearers (-2.4%)
Per 100,000 0.77
Rank movement Up 222 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #12,437 | 2,289 | 0.85 | First available Census row | First available Census row |
| 2010 | #12,953 | 2,371 | 0.80 | +82 bearers (+3.6%) | Down 516 places |
| 2020 | #12,731 | 2,315 | 0.77 | -56 bearers (-2.4%) | Up 222 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 Kilroy 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 | #12,953 | #12,731 | 1.7% |
| Count | 2,371 | 2,315 | -2.4% |
| Per 100K | 0.80 | 0.77 | -3.2% |
Between the 2010 and 2020 Census, the number of Kilroy bearers went from 2,371 to 2,315 (-2.4% change). The surname moved up 222 positions in the national ranking, going from #12,953 to #12,731.
FAQ
Kilroy surname: questions and answers
How many people in the U.S. have the surname Kilroy?
Name Census estimates that about 2,655 living Americans carry the surname Kilroy. Using the current population baseline, that works out to roughly 1 in 129,098 residents.
How common is Kilroy?
Kilroy ranks #12,731 in the 2020 Census surname tables and is classified on this site as "Rare." The Census recorded the name at a frequency of 0.77 per 100,000 residents, which is about 1 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 2,315 people with the surname Kilroy. That is different from the site's living-bearer estimate (2,655), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 0.77 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 0.77 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 1 of them to have the surname Kilroy.
Has Kilroy become more or less common over time?
Between 2010 and 2020, the surname Kilroy went from 2,371 recorded bearers to 2,315. That is a decrease of 56 (-2.4%). In the national ranking it rose from #12,953 to #12,731.
What does the Census say about the background of Kilroy?
Among Census respondents with the surname Kilroy, the largest self-reported group is White at 93.0%. The next largest groups are Hispanic (3.1%) and Two or More Races (2.2%). 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 Kilroy in the 2020 Census, accounting for 93.0% (2,153 people in the source table).
What is the full ancestry breakdown?
Kilroy appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (93.0%), Hispanic (3.1%), Two or More Races (2.2%). 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 Kilroy (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 Kilroy mean?
An Irish surname derived from the Gaelic "Mac Giolla Rua," meaning "son of the red-haired servant." 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 Kilroy (0.77 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 surname Kilroy?
HowManyOfMe.org, our sister site, answers that with the living-bearer count in one glance.