Cillian
Cillian was given to 595 boys in 2025, #507 among boys’ names; 4,090 Americans have been recorded with it since 1995 (Social Security Administration, published May 2026).
An estimated 4,060 Americans named Cillian and born in the U.S. are alive in 2026 (99% of everyone recorded); the median is 4 years old and half are between 2 and 9.
Girls and boys together; gaps are years SSA did not record (fewer than 5 births).
Births of Cillian by year: SSA national baby-name file, 1880-2025, published May 8, 2026. SSA’s notes on the data.
What does Cillian mean?
Wiktionary, Irish section
Cillian is “a male given name” Its etymology gives the senses “strife” (ceallach) and “to beat, strike” (*kelh₂-) and “monastery, church” (ceall).
Irish saint’s name, possibly derived from ceallach (“strife”) (ultimately from Proto-Indo-European *kelh₂- (“to beat, strike”)) or ceall (“monastery, church”).
/cɪˈlʲiən̪ˠ/
Meaning: Wiktionary, Irish section, as of Sep 25, 2026 (CC BY‑SA 4.0).
How popular is Cillian?
#507 among boys’ names, 2025
Cillian rose from #1,418 in 2015 to #507 in 2025 among boys’ names; its share of boys born rose from 0.06 to 0.35 per 1,000.
674 babies in 2024, the peak
Cillian peaked in 2024, when 674 babies were given it (668 boys, #463 among boys’ names). The 595 births of 2025 are 88% of that peak.
| Year | Births | Rank | Per 1,000 boys |
|---|---|---|---|
| 2025 | 595 | #507 | 0.35 |
| 2024 | 668 | #463 | 0.39 |
| 2023 | 477 | #594 | 0.28 |
| 2022 | 353 | #736 | 0.20 |
| 2021 | 341 | #747 | 0.19 |
| 2020 | 228 | #957 | 0.13 |
| 2019 | 186 | #1,078 | 0.10 |
| 2018 | 193 | #1,052 | 0.11 |
| 2017 | 170 | #1,126 | 0.09 |
| 2016 | 177 | #1,107 | 0.09 |
Every recorded year (25)
| Year | Births | Rank | Per 1,000 boys |
|---|---|---|---|
| 2015 | 121 | #1,418 | 0.06 |
| 2014 | 87 | #1,734 | 0.05 |
| 2013 | 77 | #1,852 | 0.04 |
| 2012 | 73 | #1,945 | 0.04 |
| 2011 | 66 | #2,039 | 0.03 |
| 2010 | 54 | #2,358 | 0.03 |
| 2009 | 52 | #2,457 | 0.03 |
| 2008 | 51 | #2,476 | 0.02 |
| 2007 | 39 | #2,980 | 0.02 |
| 2006 | 42 | #2,749 | 0.02 |
| 2005 | 10 | #7,200 | 0.01 |
| 2004 | 8 | #8,261 | under 0.01 |
| 2001 | 6 | #9,459 | under 0.01 |
| 1999 | 5 | #10,174 | under 0.01 |
| 1995 | 5 | #9,088 | under 0.01 |
Ranks and shares: boys’ names in each year’s SSA file; share of all boys SSA recorded that year.
Is Cillian a boy’s or a girl’s name?
Cillian has been given almost only to boys: 6 girls in 25 years of records.
Girls and boys named Cillian: the SSA national file counts each sex separately.
How many people are named Cillian, and how old are they?
4,060 alive in 2026, estimated
That is 99% of the 4,090 Americans ever recorded as Cillian. The median Cillian alive today is 4 years old; half are between 2 and 9.
The 2020 Census counted 1,410 people named Cillian (33 women and girls, 1,377 men and boys). SSA’s births carried forward to Census day, April 1, 2020, predict 1,468 born in the U.S. The Census count is 4% below that prediction.
Alive today, by age
Alive today, by generation
| Generation | Born | Alive |
|---|---|---|
| Millennials | 1981-1996 | 5 |
| Generation Z | 1997-2012 | 402 |
| Generation Alpha | 2013-2025 | 3,650 |
An estimate, not a count. SSA’s files count people born in the United States who received a Social Security number, so anyone born abroad is not in them; before 1937 most people got a number as adults, and their survival is counted from that age.
Living estimate: SSA births carried forward with the survival rates in SSA’s cohort life tables (2024 Trustees Report) for each birth year and sex. How the estimate is made. Count: Census Bureau, first names in the 2020 Census (released April 14, 2026; names reported 100 or more times, with the Bureau’s disclosure-avoidance adjustment).
Where are babies named Cillian born?
The states with the most babies named Cillian are California, New York and Texas, with 26% of its births recorded by state in 2025.
| State | Births 2025 | Rank, boys | vs. national |
|---|---|---|---|
| California | 60 | #510 | 0.8× |
| New York | 50 | #353 | 1.6× |
| Texas | 35 | #780 | 0.5× |
| Ohio | 31 | #358 | 0.9× |
| Illinois | 29 | #366 | 1.3× |
| Florida | 29 | #587 | 0.7× |
| Pennsylvania | 26 | #400 | 1.3× |
| Virginia | 25 | #330 | 1.0× |
| North Carolina | 25 | #433 | 0.7× |
| New Jersey | 24 | #345 | 1.0× |
Where Cillian is more common than its national share predicts
Relative to its national share, Cillian is most over-represented in Massachusetts: since 1995 it was given 2.5 times as often there as its national share each year would predict.
States: SSA state file, 1910-2025, published May 8, 2026; births count girls and boys together, and the rank is among boys’ names in the state in 2025. The file leaves out any state and year with fewer than 5 babies of the name, so small states are undercounted; each ratio compares the state’s births of Cillian with the births its national share predicts year by year, for states with at least 100 births of the name.
Names spelled alike
Of these 5 names spelled alike, given to 24,010 babies since 1880, Cillian is the second most given (17% of them). In 2025 it was given to 595 of their 1,584 babies (38%), again the second most given.
Spelled alike: names in the SSA national file with the same pattern of letters and sounds and at most two letters apart, and Wiktionary’s listed forms; births since 1880 and in 2025, and each name’s peak year, from the SSA national file, published May 8, 2026. Some are separate names, not spellings of one.
Names that rose and fell in the same decades as Cillian
Names whose births rose and fell across the same decades, measured on each decade’s share of births.
Similar histories: each decade’s share of births, from the SSA national file, 1880-2025, published May 8, 2026. SSA’s notes on the data.
More about Cillian and names like it
- Compare Cillian and KillianBirths, ranks, peak and the living estimate side by side.
- The most given names of the 2020sCillian peaked in 2024.
- New York’s most given namesThe state where SSA recorded the most babies named Cillian since 1910.
- Irish namesWiktionary’s origin for Cillian: every such name, by how often it is given.
- The top names of 2024The year the most babies were named Cillian.
- The names of Generation AlphaMost people named Cillian alive today were born 2013-2025.
- Names starting with CMost given first.