A criminal organization is a group run by criminals to further their illegal activities. Usually having to do with drugs, prostitution, money laundering and black marketeering. These activities are also called vice and organized crime. Some also engage in acts of political, racist, and religiously motivated violence, and in acts of terrorism and crimes against humanity.

Examples of criminal organizations would include the Yakuza (Japan), Crips, Bloods, etc. in the U.S. The role of prison gangs, by definition criminal, on activities on the outside is under-estimated by many.

Another use of the term "criminal organization" exists in human rights law and refers to an organization which has been found guilty of crimes against humanity. Once an organization has been determined to be a criminal organization, then one must only demonstrate that an individual belonged to that organization to be punished and not that the individual actually individually committed illegal acts.

The concept of the criminal organization came into being during the Nuremberg Trials. Several public sector organizations of Nazi Germany such as the SS and Gestapo were judged to be criminal organizations, while other organizations such as the German Army High Command were indicted but acquitted of charges.

This conception of criminal organizations was and continues to be controversial, and has not been used in human rights law since the trials at Nuremberg.