Recorded 1916–2025 · United States
Brennan was most popular in 2009, when 1,550 American babies were given the name — ranking #445 that year. In 2025 it ranked #1,988, with 236 births. Across 1880–2025 the Social Security Administration has recorded 35,487 people named Brennan.
Brennan first appears in Social Security Administration records in 1916, which makes it about 109 years old as a recorded American name. It has been recorded in 77 of the 110 years since.
The Social Security Administration has recorded 35,487 American births named Brennan between 1880 and 2025. That is recorded US births, not a world population — it counts people issued a Social Security number at birth in the United States. Of those, roughly 34,624 are estimated to be alive today.
236 American babies were named Brennan in 2025, ranking #1,988 that year.
Brennan is falling. Across 2021–2025 it averaged 247 births a year, against 987 a year across 2011–2015 — a change of -75% over the decade.
Measured on recorded births. American births overall have fallen since 2007, so most established names lose births over any recent decade — a name can shed births and still hold its rank. Compare the rank above, which is measured against the other names of the same year.
Across the whole record Brennan is mostly a boy’s name — 6.3% of the 35,487 Americans given it were girls and 93.7% were boys. In births since 2016 it is 8% girls and 92% boys.
Counted from every US birth the Social Security Administration recorded under this name, so it reflects use rather than opinion. A name given to fewer than five babies of one sex in a year is withheld at source and is not counted.
Roughly 34,624 Americans named Brennan are alive today — 98% of everyone ever recorded with the name. The median is 23 years old, and half are between 16 and 30.
An estimate, not a count. Recorded births are carried forward through the Social Security Administration’s 2023 period life table, by age and sex. That table describes mortality in one recent year, so it credits the oldest cohorts with today’s survival rather than the harsher rates they actually lived through — the further back a name peaked, the more this will overstate how many remain. It counts people issued a Social Security number at birth, not immigrants who arrived later.
How much more common the name is in each state than across the country as a whole.
See Brennan on the interactive charts
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Source: U.S.A. Social Security Administration. Years 1880–2025. namelegacy.org