Nacht und Nebel, meaning Night and Fog, also known as the Night and Fog Decree, was a directive issued by Adolf Hitler on 7 December 1941 targeting political activists and resistance "helpers" in the territories occupied by Nazi Germany during World War II, who were to be imprisoned, murdered, or made to disappear, while the family and the population remained uncertain as to the fate or whereabouts of the alleged offender against the Nazi occupation power. Victims who disappeared in these clandestine actions were often never heard from again.

An enforced disappearance is the secret abduction or imprisonment of a person with the support or acquiescence of a state followed by a refusal to acknowledge the person's fate or whereabouts with the intent of placing the victim outside the protection of the law. Often, forced disappearance implies murder whereby a victim is abducted, may be illegally detained, and is often tortured during interrogation, ultimately killed, and the body disposed of secretly. The party committing the murder has plausible deniability as there is no evidence of the victim's death.