Child molestation (sexual assault or abuse) is generally defined as physical contact or other interaction between a child (under age 17, for example) and an adult when the child is being used for the sexual stimulation or pleasure of the perpetrator or another person. In addition to physical contact, child molestation may include (1) the exposure of the genitals of an adult in the presence of a child, (2) the exposure of the genitals of a child, (3) using a child in making pornography, or (4) making a child view sexual acts or pornography.

Child molestation laws vary from state to state, and criminal charges for child molestation and related crimes are sometimes called (1) sexual assault of a child, (2) aggravated sexual assault of a child, (3) sexual abuse of a child, (4) indecency with a child, (5) sexual performance by a child, (6) sexual trafficking of a child, or (7) prostitution of a child.

In some states multiple instances of sexual contact between an adult and a child may constitute the enhanced criminal offense of continual sexual abuse of a child—which is sometimes a first-degree felony offense.

Child molestation laws are usually included in a state’s penal or criminal code (statutes)—which provide for the related criminal charges—and in a state’s family code (statutes) that address the civil (non-criminal) implications of child molestation—often in the context of divorce and child custody matters.

Except in limited circumstances, federal laws generally do not apply to child sexual abuse matters that take place within a single state—without transportation of the child or other materials (photographs, videos, etc.) across state lines. Such criminal matters that take place within a single state are generally handled by state or local authorities and prosecuted under state laws. But if the sexual abuse or molestation of a child involves conduct or materials in multiple states, or occurs on federal lands (military bases, American Indian territories) the offense may be prosecuted under federal law.

In California, child molestation, which encompasses a range of behaviors including inappropriate physical contact, exposure, and exploitation of children in pornography, is addressed under various sections of the state's penal code. The age of a child in California is defined as anyone under the age of 18. Crimes such as lewd acts with a minor (California Penal Code 288), sexual exploitation of a child (California Penal Code 311.3), and using a minor for sex acts (California Penal Code 311.4) are examples of charges that may be applied in cases of child molestation. California also recognizes the offense of continuous sexual abuse of a child (California Penal Code 288.5), which involves repeated sexual conduct with a child and is a serious felony. These laws are enforced by state or local authorities, and the state's family code also addresses the civil implications of child molestation, particularly in family law matters such as divorce and child custody. Federal law may apply if the offense involves crossing state lines, involves multiple states, or occurs on federal lands, but otherwise, child molestation is typically prosecuted under state law.