Ildefonso is a rare boys' name that peaked in 1976 and has since faded.
Ildefonso is a boy name. It last appears in U.S. records in 2022. Ildefonso first appears in 1917 and peaked in 1976 (16 births).
| Year | U.S. births | U.S. + territories | Rank |
|---|---|---|---|
| 2022 | 5 | 5 | #13,074 |
| 2011 | 5 | 5 | #13,038 |
| 2008 | 5 | 5 | #13,283 |
| 2006 | 6 | 6 | #11,167 |
| 2005 | 5 | 5 | #12,108 |
| 2004 | 5 | 5 | #12,033 |
| 2003 | 7 | 7 | #9,024 |
| 2001 | 6 | 6 | #9,725 |
| 1999 | 8 | 8 | #7,421 |
| 1997 | 10 | — | #5,811 |
| 1996 | 7 | — | #7,442 |
| 1994 | 5 | — | #9,365 |
| 1993 | 10 | — | #5,511 |
| 1992 | 11 | — | #5,016 |
| 1990 | 7 | — | #6,709 |
| 1989 | 8 | — | #5,858 |
| 1988 | 6 | — | #6,739 |
| 1987 | 6 | — | #6,423 |
| 1986 | 8 | — | #5,052 |
| 1985 | 8 | — | #4,870 |
| 1984 | 6 | — | #5,871 |
| 1983 | 12 | — | #3,495 |
| 1982 | 10 | — | #4,063 |
| 1981 | 7 | — | #5,154 |
| 1980 | 5 | — | #6,645 |
| 1979 | 7 | — | #5,046 |
| 1978 | 8 | — | #4,311 |
| 1976 | 16 | — | #2,646 |
| 1975 | 8 | — | #4,094 |
| 1974 | 6 | — | #4,871 |
| 1973 | 11 | — | #3,102 |
| 1972 | 6 | — | #4,661 |
| 1970 | 5 | — | #5,032 |
| 1968 | 5 | — | #4,386 |
| 1967 | 7 | — | #3,383 |
| 1966 | 10 | — | #2,701 |
| 1965 | 6 | — | #3,696 |
| 1964 | 9 | — | #2,947 |
| 1963 | 6 | — | #3,812 |
| 1962 | 9 | — | #2,932 |
| 1961 | 9 | — | #2,987 |
| 1960 | 8 | — | #3,195 |
| 1959 | 6 | — | #3,770 |
| 1954 | 11 | — | #2,520 |
| 1952 | 7 | — | #3,219 |
| 1948 | 8 | — | #2,882 |
| 1947 | 7 | — | #3,216 |
| 1946 | 10 | — | #2,474 |
| 1940 | 5 | — | #3,682 |
| 1931 | 6 | — | #3,576 |
| 1928 | 6 | — | #3,919 |
| 1924 | 6 | — | #4,100 |
| 1917 | 6 | — | #3,747 |