Riannon has been given to about 250 people in the United States since 1880. It was most common in 1987, which makes it a Gen X and millennial name.
Its best year was 1987, when 14 babies were given the name, ranking 5542nd. The typical living American called Riannon is about 34 years old today.
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.