Seiji is a rare boys' name that peaked in 2007 and has grown less common since.
Seiji is a boy name. In 2025 it ranked #9,569 for boy births in the United States (and #19,765 across all names), given to 8 babies. Seiji first appears in 1914 and peaked in 2007 (19 births).
| Year | U.S. births | U.S. + territories | Rank |
|---|---|---|---|
| 2025 | 8 | 8 | #9,569 |
| 2024 | 8 | 8 | #9,722 |
| 2023 | 9 | 9 | #8,809 |
| 2022 | 7 | 7 | #10,665 |
| 2021 | 7 | 7 | #10,599 |
| 2020 | 10 | 10 | #7,953 |
| 2019 | 5 | 5 | #13,805 |
| 2018 | 6 | 6 | #11,898 |
| 2017 | 12 | 12 | #7,029 |
| 2016 | 7 | 7 | #10,550 |
| 2015 | 11 | 11 | #7,437 |
| 2014 | 12 | 12 | #6,986 |
| 2013 | 10 | 10 | #7,999 |
| 2012 | 15 | 15 | #5,942 |
| 2011 | 16 | 16 | #5,636 |
| 2010 | 12 | 12 | #7,024 |
| 2009 | 7 | 7 | #10,780 |
| 2008 | 13 | 13 | #6,701 |
| 2007 | 19 | 19 | #4,951 |
| 2006 | 14 | 14 | #6,041 |
| 2005 | 13 | 13 | #6,159 |
| 2004 | 10 | 10 | #7,432 |
| 2003 | 11 | 11 | #6,647 |
| 2002 | 12 | 12 | #6,009 |
| 2001 | 10 | 10 | #6,855 |
| 2000 | 7 | 7 | #8,973 |
| 1999 | 10 | 10 | #6,435 |
| 1998 | 9 | 9 | #6,745 |
| 1997 | 11 | — | #5,587 |
| 1996 | 8 | — | #7,003 |
| 1995 | 13 | — | #4,739 |
| 1994 | 5 | — | #9,990 |
| 1993 | 5 | — | #9,921 |
| 1992 | 9 | — | #6,054 |
| 1990 | 5 | — | #9,274 |
| 1989 | 9 | — | #5,523 |
| 1985 | 8 | — | #5,070 |
| 1984 | 5 | — | #7,142 |
| 1982 | 9 | — | #4,528 |
| 1979 | 8 | — | #4,782 |
| 1978 | 5 | — | #6,605 |
| 1977 | 5 | — | #6,699 |
| 1974 | 5 | — | #5,875 |
| 1970 | 5 | — | #5,321 |
| 1939 | 5 | — | #3,902 |
| 1938 | 6 | — | #3,482 |
| 1937 | 6 | — | #3,475 |
| 1934 | 5 | — | #4,132 |
| 1929 | 8 | — | #3,213 |
| 1927 | 5 | — | #4,703 |
| 1926 | 8 | — | #3,343 |
| 1925 | 12 | — | #2,565 |
| 1924 | 11 | — | #2,798 |
| 1923 | 11 | — | #2,750 |
| 1922 | 8 | — | #3,489 |
| 1921 | 5 | — | #4,876 |
| 1920 | 6 | — | #4,207 |
| 1919 | 5 | — | #4,705 |
| 1917 | 5 | — | #4,487 |
| 1914 | 6 | — | #3,212 |