Upskirting is the act of secretly or surreptitiously photographing underneath a woman’s dress or skirt. Because upskirting often occurs in public places, laws prohibiting the practice have been challenged on the ground that the victim does not have a reasonable expectation of privacy.

Laws regarding upskirting behavior—including photographing or videotaping a person in a bathroom or changing room—vary from state to state. In some states this conduct is prosecuted as a criminal offense under invasion of privacy, voyeurism, unlawful surveillance, surreptitious recording, disorderly conduct, or public lewdness statutes—depending on the state and its current laws.

Upskirting and the related criminal offenses for which upskirting may be prosecuted are located in a state’s statutes—often in the penal or criminal code.

In Montana, upskirting is considered a violation of privacy and is addressed under the state's voyeurism laws. Montana Code Annotated (MCA) 45-5-223 specifically prohibits the act of surreptitiously recording or photographing a person's intimate areas when that person has a reasonable expectation of privacy and without that person's knowledge or consent. This includes upskirting, which is the act of taking unauthorized photographs or videos underneath a person's clothing to view their intimate areas. The law applies regardless of whether the act occurs in a public or private place. Violation of this statute is a serious offense and can result in criminal charges ranging from a misdemeanor to a felony, depending on the circumstances and whether the offender has prior convictions for similar offenses.