Reilly has been given to about 10,088 people in the United States since 1880. It was most common in 1997, which makes it a Gen X and millennial name.
Its best year was 1997, when 543 babies were given the name, ranking 623rd. The typical living American called Reilly is about 22 years old today. It is relatively most common in New Jersey, where it accounts for 0.01% of births.
Source: US Social Security Administration, national and state name files, 2025 release, and the Office for National Statistics for England and Wales. Etymology researched and written by our editors. Living-population and median-age figures are our own estimates, described in the methodology.