Ildefonso is a distinctive boys' name in United States, ranking #13037 in 2011 with 5 recorded births. The name reached its all-time peak in 1997 with 10 births ranking #5811. Since 1996, the popularity has decreased by 28.6%. In 2011, approximately 1 in every 379,798 boys born was named Ildefonso. STABLE Recent data shows the name is currently stable.