In law, a false allegation is one in which a person deliberately accuses another person of a crime that he did not commit and does so with full knowledge that the accused person is not guilty of that crime. It is often made as a form of revenge, an attempt to divert attention away from a guilty party, or as a way for the accuser or accusers to prevail in an ongoing dispute. In the media, false allegations are often connected with various types of sexual crimes and misconduct, but it is not unusual for people to be accused of all different sorts of wrongdoing. The penalty for making false claims about a person's behavior varies by jurisdiction, but may in some places be treated as a crime in itself. Victims of false accusations may also decide to sue their accusers in order to receive some compensation for the damages they sustained.

Although most people do not abuse the criminal justice system, some unscrupulous individuals will make false reports about others in order to intimidate, harass, and upset their targets. Being confronted by law enforcement is usually a very distressing experience for most people, so a false allegation can be a very effective way of hurting another person. Even worse, victims of false allegations may be the subject of negative attention both in the media and in their community and social circles. As it can be difficult to undo the effects of a false allegation, victims of this practice may have a great deal of difficulty restoring their good name and counteracting damage done to their career and relationships as a result of being held in suspicion.

One of the difficulties in handling a false allegation is that there are cases in which it is impossible to prove beyond a reasonable doubt that someone has committed a crime even if he or she is in fact guilty. As such, law enforcement may be reluctant to pursue a case against somebody who has made a false accusation because there is the possibility that the accusation was in fact sincere but that there is little evidence to back up the claims. After investigation, however, it may appear that an allegation was not made in good faith, and the police and prosecutors may choose to criminally charge the accuser. The accused may also decide to sue her accuser for making up the false allegation in order to both clear her name and to receive some compensation for the damage caused by the accusations.