Except for some rare exceptions, you must be 18 years old to file Form N-400, Application for Naturalization.
However, it is possible for permanent resident children to become U.S. citizen through a parent in a process known as derivation.
Under Section 320 of the Immigration and Naturalization Act, also known as the Child Citizenship Act of 2000, children under 18 automatically acquire U.S. citizenship if the following three conditions have been fulfilled:
- At least one of the child’s parents is a U.S. citizen by birth or naturalization;
- The child is a permanent resident under 18 years of age;
- The child is residing in or has resided in the United States in the legal and physical custody of the U.S. citizen parent.
Learn more in Derivation of U.S Citizenship for Children.