How Many People Are Named Cillian?
An estimated 3,467 people in the United States have the first name Cillian. It is almost exclusively a male name. The average bearer is 7 years old, and Cillian peaked in popularity in 2024 with 674 births that year.
Below you will find a full statistical profile of Cillian as a first name in the United States, including gender data, a year-by-year popularity timeline going back to 1880, a decade breakdown, and state-by-state birth registrations. You can also check how many people share the full name Cillian paired with any surname.
Key Insights
- Cillian is a modern name. With an average bearer age of just 7, it has gained most of its popularity in recent years.
Estimated Living Americans
3,467
About 1 in 98,862 people in the U.S.
Rarity
Rare
Predicted Gender
Male
99.8% confidence
Average Age
7
years old
Peak Year
2024
674 births
Total Registered
3,492
since 1880
Gender Distribution for Cillian
Cillian is almost exclusively a male name. Out of 3,492 total births registered, 99.8% were male.
Cillian as a male name
Ranked #463 in 2024
668 male births in 2024
Peak: 2024 (668 births)
Cillian as a female name
Ranked #13,797 in 2024
6 female births in 2024
Peak: 2024 (6 births)
Cillian: Popularity Over Time
SSA records for Cillian span from the 1990s to the 2020s, covering 4 decades of naming data. The most popular decade for this name was the 2020s, when 2,070 babies were registered. Cillian remains highly popular today, with recent registration numbers near its historical peak.
Cillian by Decade
How has Cillian tracked across different eras? The table below groups all SSA birth registrations into 10-year periods, with separate male and female counts. The colored bar shows each decade's share relative to the peak.
Cillian by State
Birth registrations for Cillian span all 37 states and territories in the SSA database. The highest counts are in New York, California, Massachusetts. The lowest are in Rhode Island, Maine, Alaska. On average, about 70 Cillians were registered per state.
Cillian + Last Name Combinations
How many people share a full name with Cillian as the first name? Click a combination below to see the estimate, or search any pairing.
Names Similar to Cillian
Other first names starting with C with a similar number of bearers.
Cillian: Questions and Answers
How many people in the U.S. are named Cillian?
We estimate approximately 3,467 people named Cillian are alive in the United States today. This is based on SSA birth records from 1880 to 2024, adjusted for mortality using CDC life tables. About 1 in 98,862 Americans share this first name.
Is Cillian a common name?
Cillian is classified as "Rare" and is more popular than 95.6% of all first names in the SSA database. A total of 3,492 births have been registered with this name since 1880.
When was Cillian most popular?
Cillian reached peak popularity in 2024, when 674 babies were given this name. The average age of a living person named Cillian is approximately 7 years old, reflecting when the name was most commonly given.
Is Cillian a male name?
Cillian is predominantly male. 99.8% of people with this name are male. See the gender breakdown above for full details.
How many Cillian Smiths are there?
To find how many people share a specific full name, we combine first name and surname frequencies. Try: Cillian Smith, Cillian Johnson, Cillian Williams. You can also search any combination on our homepage.
Where does this data come from?
Our estimates use Social Security Administration birth records (1880 to 2024), adjusted for survival using CDC 2023 life tables broken down by sex. The U.S. population figure (342,754,338) is from the Census Bureau's July 2025 estimate. Full methodology.
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